Hot Rod Forum : Hotrodders Bulletin Board - View Single Post - Fuel/firing Problems with Fuel Injected TPI engine 87 camaro z28
View Single Post
  #3 (permalink)  
Old 07-09-2003, 07:25 PM
trees trees is offline

Last journal entry: JB's 37 Pickup
Last photo:
Join Date: Oct 2002
Location: Smoky Mountains
Age: 78
Posts: 2,358
Wiki Edits: 0

Thanks: 0
Thanked 3 Times in 3 Posts
Hmmmmnn. Sparkplugs in a running engine should never be wet. What kind of test were you supposed to be doing that would result in wet spark plugs? The 87 IROC is the first year of the 350 TPI, I believe, and it was a "batch fire" system. You should have 24# per hr injectors and your fuel pressure should be regulated to 41-43 PSI. You have completed a pretty logical sequence of checks and replacements to this point. Now I would check the fuel pressure with the engine running. Be sure the guage is hooked up before start and you disconnect after shut down. If pressure is good, then you need to read your engine codes. Auto Zone, Pepboys etc should be able to help you with this to see if you have some obvious problems. Then you want to look at your Throttle Position Sensor (TPS) You check it with an ohm meter and look for for _.4 to +.2 ohms at the engine off,idle position. Then move the throttle smoothly to the WOT position and back to idle, watching for the ohmmeter to increase/decrease smoothly with the throttle. This is the usual suspect for a poorly running TPI since it works a bunch for normal driving, especially city driving. Next would be your Mass Ai Flow Sensor (MAF) which is in the air inlet before the air cleaner. Then the last would be your oxygen sensor, which is a plug with wire (s) in the exhaust pipe just after the exhaust manifold. The above mentioned parts stores should be able to tell you if your system is in open or closed loop. It should be in closed loop. If it is in open loop, you need to replace the 02 sensor because the engine will run too rich in the open loop mode. There are two sensors that seldome fail and that is the inlet air temp and the coolant temp ( normally seperate from your coolant temp guage sensor). The MAF, 02 and TPS are expensive enough that you do not want to start replacing them unless you have a known failure.

Good luck.

Reply With Quote