Hot Rod Forum : Hotrodders Bulletin Board - Reply to Topic
Hotrodders.com -- Hot Rod Forum



Register FAQ Search Today's Posts Unanswered Posts Auto Escrow Insurance Auto Loans
Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Engine> '89 5.7 TBI stumble/dying on light acceleration
User Name
Password
lost password?   |   register now

Thread: '89 5.7 TBI stumble/dying on light acceleration Reply to Thread
Title:
  
Message:
Trackback:
Send Trackbacks to (Separate multiple URLs with spaces) :

Register Now

In order to be able to post messages on the Hot Rod Forum : Hotrodders Bulletin Board forums, you must first register.
Please enter your desired user name (usually not your first and last name), your email address and other required details in the form below.
User Name:
If you do not want to register, fill this field only and the name will be used as user name for your post.
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Additional Options
Miscellaneous Options

Topic Review (Newest First)
02-21-2013 10:14 AM
oldbogie
Quote:
Originally Posted by Trainwreck View Post
The truck is FINALLY running great, got the stumble/ hesitation figured out. It has been a learning experience to say the least. Before I explain what I found, I want to thank everybody that jumped in to help me with this problem. you're a great bunch of folks!!

I was out of ideas on what to do on the truck so I bit the bullet and had a tech come out to the house and bring his computer/scanner/artificial intelligence thingamabob.

An hour and half later his advice was to replace the ECM and the muffler! He said the ECM wasn't modulating the pulse width on the EGR, it was signalling the solenoid to open and stay open at any throttle position above idle. His exhaust advice was that the Magnaflow muffler (the only non-stock component in the exhaust system) was causing insufficient back-pressure and messing up the EGR valve.

I thanked him, paid him and sent him away. I wasn't convinced of his diagnosis but went to the wrecking yard and picked up a compatible ECM off a running truck that had the top crunched by a fallen tree. I installed it with no change in symptoms. I just could not accept that the muffler was causing my problem so I ignored the 'replace it' advice. After thinking about it for a couple of day, I decided to go talk to my local parts house about EGR valves. The guy looked up my truck and said that there were two available- one for 8500 lbs. GVWR and lower and one for above 8500 lbs. GVWR. He had both in stock and pulled them out to look at them, they were noticeably different in their design. The light bulb came on over my head and I went home and looked at my engine's EGR valve. My truck is a 8500 and lower truck but had the 8500 and above EGR on it. I went to the wrecking yard again and grabbed an EGR off another truck that matched what I needed. I installed it and...... it runs like a top, 50 miles of around town driving without any issues at all!!

The EGR valve was passing all the tests because it was not broken, it was just the wrong one for my application. What an ordeal! But I'm happy- the truck is running like it should and my blood pressure back down to a reasonable level.
Trainwreck, that didn't occur to me; it should have. Yes there are two different EGRs and they are not interchangable insofar as the program on the PCM is concerned. It didn't occur to me that there could be a miss match or even a failure of the proper EGR which will look a lot like an injector problem.

The computer is looking for a temperature of the EGR valve, a go/no-go check if it gets hot enough you don't get a code if it doesn't you do. The code or lack there-of doesn't mean it's operating properly only that it gets hot which means exhaust is flowing through it. It's common when putting headers and or duals on these TBI engines to see the EGR failure code illuminate because the reduced back pressure doesn't feed enough exhaust through the valve to heat it up to the expected temperature.

Bogie

My bad and thanks for the heads-up reminder.

Bogie
02-20-2013 10:12 AM
bigbadgordy what causes a throttle body inj to stumble cut out and it cuts in and out
07-27-2012 10:14 PM
HDLewis
EGR? Where is it located?

A friend e-mailed me this thread after my problems with my truck recently. I love my truck but don't have a lot of mechanical experience. I recently had the fuel pump, fuel pressure regulator, and fuel filter replaced. Runs good in general, but when I take off periodically it has hesitation, almost like I'm in water. It doesn't happen everyday or all the time. After reading your thread, I'm beginning to think I need to check/change the EGR. My problem is knowing where it's located on my vehicle. When I do find it, can I clean it or is it better to just replace it (new or used). I bought it used last year and it's run great for me until last month. I originally replaced the parts because as I would give it gas it would bog down without quite dying, then I was able to feather my gas pedal back up to speed. Replacing the fuel pump etc. got me back on the road but now I am still having the same problem. PLEASE HELP! I want to try replacing the EGR, I just need to know where to find it and I need to know how to replace it. My truck is a 2000 Chevy C2500 3/4ton.
06-08-2010 01:19 AM
chop88top
tbi problems

Hey everyone,

Im working on a 93 Motorhome with 7.4 TBI. Will not start with MAP sensor plugged in. Unplug it and will run but like crap. Repaired the wiring harness that was damaged by the compressor and replaced MAP so far. THinking the wiring damage shorted the ECM?

Thanks
06-05-2010 09:53 PM
Duntov You're right There will be a "next guy" with a similar bug. That's what this forum is all about......... That and free speech... I'll keep kicking in a couple of bucks on a regular basis...

I think we got the same muffler guy... Duntov
06-05-2010 09:21 PM
Trainwreck
Quote:
Originally Posted by Duntov
EGR was a surprise. I was betting on Bogie's direction. I've seen the replacement of worn injectors improve idle and overall performance and fuel mileage on that series of truck several times in the last couple of years. Now you can Ebay your extra ECM I've also seen some of those go recently. Should be a market for one, especially with your brief of the recent history on it.
ECM- I'm thinking I'll hold on to it as a spare, it seems they have some problems occasionally.

Exhaust- I think every Chevy truck in my home town has a performance muffler on it, I just couldn't believe it would be my problem (plus a quick chat with my favorite muffler shop that went like this- "blah, blah, blah" (me explaining problem), they said (and I quote) "what a load of *****, look for something else". Gotta love a guy that gets to the point!

As I searched the 'net for answers I found tons of posts in several forums dealing with this kind of problem but I had trouble finding specific testing info and what were good test results and bad test results. So I have tried to be as complete as possible with my descriptions of the problem and the things that were tried in the attempt to figure it out, hoping that it will help out the next guy who has a similar bug.

Thanks again guys!
06-05-2010 02:06 PM
GMCTRUCKS
EGR valve.

I was having problems with my trucks EGR and went to get my emissions test and it didn't pass because of high NOX so I changed out my EGR with a used one and she passed with flying colors but the EGR was from a different year truck and my buddy told me it might have a hesitation because the EGR might have a different orifice size than yours and sure enough it did because it was doing the same thing yours was.

So I replaced it with a new one and she runs super now. I hope this thread helps a lot of people. And yes there is different ones for the weights of trucks.
06-05-2010 01:53 PM
ChevyTruckGuy You need to go Here! www.fullsizechevy.com
Craig
06-05-2010 12:30 PM
DoubleVision This kind of reminds me of mine which is a 92 chevy with a rebuilt 4.3
Upon tear down to get the rebuild process going, I stupidly threw the original EGR valve away. When I bought one when the engine was ready to go back in, I realized the new valve came with a washer restrictor kit that your supposed to match up with the original sized valve, but I had also did a exhaust mod so it was more free flowing so I took a stab at it what size washer to use. After all was said and done, the truck ran like crap. It kept kicking on the code that indicates the MAP sensor was bad. After replacing it with no change, I started disconnecting stuff hoping I could isolate where the problem was. I unplugged the EGR and capped the line. Afterwards it ran great and the MAP sensor code was gone. Ever since then I`ve left it like that. The only time it gets a code now is EGR failure every now and then.
06-05-2010 11:43 AM
KMatch
Quote:
Originally Posted by Trainwreck
The EGR valve was passing all the tests because it was not broken, it was just the wrong one for my application. What an ordeal! But I'm happy- the truck is running like it should and my blood pressure back down to a reasonable level.
Look at the "faulty" egr valve where the vac line attaches. The right one will have a pinhole sized restriction slowing the vacuum while the wrong one will have a wide open vacuum port. The wide port causes what you're describing as once the EGR gets a signal, it slams open causing the stumble. The right one will use the vacuum restriction while the aftermarket ones will also use washers to regulate the exhaust flow at the base of the valve.

As for your tech buddy, the backpressure type egr valves are more sensitive with more backpressure. Less backpressure and the valve is less sensitive. The magnaflow might cause a code 32 (worst case, not likely as in nearly impossible scenario) but won't cause the valve to work as he described. You've just witnessed a "parts tosser" tech. Thump him for me.
06-05-2010 09:42 AM
Duntov
Egr

EGR was a surprise. I was betting on Bogie's direction. I've seen the replacement of worn injectors improve idle and overall performance and fuel mileage on that series of truck several times in the last couple of years. Now you can Ebay your extra ECM I've also seen some of those go recently. Should be a market for one, especially with your brief of the recent history on it.
06-04-2010 10:10 PM
Trainwreck The truck is FINALLY running great, got the stumble/ hesitation figured out. It has been a learning experience to say the least. Before I explain what I found, I want to thank everybody that jumped in to help me with this problem. you're a great bunch of folks!!

I was out of ideas on what to do on the truck so I bit the bullet and had a tech come out to the house and bring his computer/scanner/artificial intelligence thingamabob.

An hour and half later his advice was to replace the ECM and the muffler! He said the ECM wasn't modulating the pulse width on the EGR, it was signalling the solenoid to open and stay open at any throttle position above idle. His exhaust advice was that the Magnaflow muffler (the only non-stock component in the exhaust system) was causing insufficient back-pressure and messing up the EGR valve.

I thanked him, paid him and sent him away. I wasn't convinced of his diagnosis but went to the wrecking yard and picked up a compatible ECM off a running truck that had the top crunched by a fallen tree. I installed it with no change in symptoms. I just could not accept that the muffler was causing my problem so I ignored the 'replace it' advice. After thinking about it for a couple of day, I decided to go talk to my local parts house about EGR valves. The guy looked up my truck and said that there were two available- one for 8500 lbs. GVWR and lower and one for above 8500 lbs. GVWR. He had both in stock and pulled them out to look at them, they were noticeably different in their design. The light bulb came on over my head and I went home and looked at my engine's EGR valve. My truck is a 8500 and lower truck but had the 8500 and above EGR on it. I went to the wrecking yard again and grabbed an EGR off another truck that matched what I needed. I installed it and...... it runs like a top, 50 miles of around town driving without any issues at all!!

The EGR valve was passing all the tests because it was not broken, it was just the wrong one for my application. What an ordeal! But I'm happy- the truck is running like it should and my blood pressure back down to a reasonable level.
05-21-2010 11:22 AM
oldbogie
Quote:
Originally Posted by Trainwreck
I recently finished up a rebuild on my 1989 C2500 TBI 5.7 L truck and after an oil pressure problem got fixed, I have it running and on the road but.... I've been trying to figure out a problem with stumbling, hesitating, and dying. It has been going on from the first time I drove it after the rebuild.
The truck hesitates and stumbles BAD when I lightly apply the throttle. If I put my foot in it when leaving a stop it will accelerate okay but if I just ease away in a normal fashion it will stumble, buck, and even die if I don't get deeper into the pedal. I thought I had it fixed after replacing the EGR solenoid but qapparently not. I drove to town this morning and the problem is still happening. I nursed it to the parts store and, since it is the only thing I could think of, bought a new ($60) TPS. I got home and installed the TPS and went for a drive. No change at all. I'm completely baffled.
Here is what I have done so far:

Fresh build on engine- 250 miles so far
New plugs
New plug wires
New cap
New rotor
New fuel filter
New air filter
Timing set to 0 degrees with tan wire unplugged per the book
No vacuum leaks- checked every line and around throttle body with propane
Fuel pressure rock solid at 12.5 psi
EGR valve tested and passed
New MAP sensor
New EGR solenoid
New Throttle Position Sensor
New Coolant Temperature Sensor

Truck runs fine when cold, problem becomes noticeable as engine approaches normal temp.
Anybody got any suggestions?
The injectors are aging out, they're just not operating well when the flow demand is low, probably not shutting the fuel flow off completely so they run a bit rich for the low speed condition where there is more "closed" time in relation to open., so the dribble is a bigger proportion of the total fuel demand. You don't see it when the engine is cold and running on "choke" as the engine wants to rich at this point; then don't see it again when the RPMs or power demand is higher as the injector is passing the off phase so quickly that the dribble is inconsequential against the total flow and the computer can probably still trim for it so it isn't throwing any codes.

I'd start with a couple doses of injector cleaner, if that doesn't improve it, then some rebuilt injectors are in order.

Bogie
05-21-2010 07:42 AM
gizmo-1948 The next thing to check would be all your wire connections, make sure that all the connectors are completely snapped in place, and that none of the wires have been pushed out, especially at the distributor. Next, I would unplug the EGR valve at the valve and plug the hose with a golf tee or similar and take it for a test drive to isolate that system from your problem, new parts or not. If problem persists, I would attach my timing light, leaving the by-pass hooked up, vary the RPM and confirm that your timing is changing. If I remember correctly, when you hook the by-pass wire back up and recheck timing, it should be sitting on about 10 degrees advance. If the timing is not changing, except for centrifugal at higher RPM's I would suspect the ignition module.
05-20-2010 08:22 PM
Trainwreck Yes I did, as I remember it was un-moved. This only my second TBI powered truck, the first one was a '90 1 ton w/ 454. Never had a problem with it so I'm learning as I go here. This one is whuppin' my arse.
This thread has more than 15 replies. Click here to review the whole thread.

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


All times are GMT -6. The time now is 11:27 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.