I recently got a 1987 Iroc Z 205tpi 5 speed. The car has the edlbrock ti-tech headers on it,a TPIS intake,3 inch flowmaster exhaust.The car has an idling problem..its runs but bounces around.The spark plugs are all white..That indicates lean right?I'm thinking of getting new injectors,now the stock ones are 19lbs..should I go to say 21lb ones since plugs are white and with the bolt on extras?I'm not sure if its as simple and just buying 21lb and sticking them in or do I have to do something to the ECM so it knows there bigger?Thanks I'm new to 3rd generations used to working on holleys and Q-jets..

 

If they are ALL white, as in the metal parts around the tip are coated in white, then that indicates a fuel problem. I would first check the fuel pressure at idle and under load.
Excessive heat, combustion heat or metal heat can cause the plugs to be white as well. If the whole engine were running hot, then you should see this on your temp gauge. Check your cooling system. Also check to make sure your CAT isn't plugged, though that usually results in sooted plugs.

Replacing the injectors isn't necessarily the proper fix. The 19 lb injectors are correct for the 305, but 21 lb/hr isn't so far off that the system can't compensate to a degree using negative BLMs.

The correct route is to fix the fueling or heat problem, then if you want to upgrade the injectors, get the larger ones, then change the injector constant on the PROM to match them. I suggest datalogging the whole time before and after so you have a comparison.

 

ok,thanks.The engine isn't getting hot and the radiator fluid is nice and green no rust at all.Never really climbs over 200 much if any.As for checking the fuel pressure can i do that at the port on the fuel rails?Also how do you do it on a tuned port car,I'm new at this... feel stupid... but need to know these things.Also what should the pressure be at?I'm gonna ohm the injectors out tomorrow to see if there is a bad one.Thanks

 

Yes, port on the fuel rail. Stock is 43 PSI, but normal range is from 38 to 43 PSI at idle, and 47 to 50 PSI with vacuum removed from the regulator (fully loaded). For loaded driving run the gauge up to the windshield so you can watch it.

 

If it has headers and a intake it might have a cam also. That's the problem with getting a "new" car. Best way is if there are no mechanical problems would be to see what the exhaust is with a exhaust analyzer or a wideband O2 sensor. That will tell you rich or lean and you can go from there after OHMing the injectors.

 

Be sure to listen to each injector using a screwdriver too. You should be able to hear/feel a pulse from each one. It's possible that you could have a bad injector that still ohms correctly.

 

 

You can also pull the plugs, if you have a wet cylinder you have a leaky injector.

www.southbayfuelinjectors.com

 

ok thanks guys..I changed the fuel filter today... it said AC DELCO and the car has 157,000 on it so it was do..lol.better late then never i guess.Now I was driving it around and got a check engine light..code 22 so that points to TPS switch or voltage to TPS..I think thats just another issue though..that wouldn't make the car miss would it?Its erroring to the high RPM side not closing up and choking the engine.It go from 1500 rpms to 750 sometimes..hey what do you want I got the car for FREE..I'm gonna pick up a new TPS anyway since there are fairly cheap.

 

22. Low voltage at throttle positon sensor OR Fuel cutoff relay circuit open or shorted to ground

You can easily check the voltage to the TPS with a DVOM before you go and buy another one.

 

ok there are 3 wires on the TPS switch..which two do I test with the meter to check voltage?Also what should it be around,if its grounding out then I'm assuming check for bare wires etc..is that correct?

 

nevermind I just found a link doing a search this forum..