I'm trying to track down the source of my surging/hunting idle problem with my 1991 MAP TPI L98 350 installed in my 1991 RX-7 convertible.

Here are the symptoms:

When the motor is cold it runs OK with the exception of a small misfire When the motor is warmed up, the idle RPM starts surging at a constant rhythm.

What I've checked/tried:

no codes in field service mode from the ECM (but I don't have a scanner)

I haven't found any obvious vacuum leaks

Adjusted the TPS and it reads .54 volts (.54 is the closet to .5 volts it will adjust to).

During the surging I have unplugged the IAC and it has no effect on the surging/hunting idle problem.

During the surging if I reach up under the plenum and push up on the EGR diaphragm the surging stops.

I checked the fuel injector OHM values while the motor was warm and found them at
12.3 ... 17.8 .... 7.9 .... 11.5 ... 5.5 .... 11.8 .... 17.6 and 10.5 ohms

My question:

Since the injector ohm values are so out of whack ... I'm guessing the injectors are probably causing the misfire, but can bad injectors also cause the surging/hunting idle problem?

Or are the 2 problems unrelated? and if so is there anything else I can try or check?

thanks for any help

 

Well for starters, your tps is supposed to be set at .54 + or - .08 volts with throttle closed. If you have it set at 5 volts, that is waaaaaaay to high and most likely your problem. Also, if your readings are correct on your injectors, you need to replace at least four of them. If you do replace the four of them, you might as well replace all eight of them with a good set injectors that are more closely matched.

The Trickster!!!!!!!!!!!!

 

I don't know if a bad injector/injectors would cause a surging idle, never heard of that being the case before but ya never know.

What about your minimum air setting? I had a problem with surging idle after swapping TBs and upon setting the min air it went away.

 

Actually thats the exactly what was happening to me, it was explained to me that this would happen because with the injectors being bad/going bad they were all/some trying to compensate. Therefore causing the engine to surge.

I replaced all 8 injectors and the problem cleared right up.

 

Injectors. All are suppose to be around 16 i believe.

 

Also try cleaning and resetting the IAC.

 

Good to know!

 

My Haynes Book says the injectors should be 11.0 - 14.0 ohms.?

My injectors are ranging from 5.5 - 17.8 ohms. so I'm guessing my injectors are shot.

my biggest fear is disassembling the TPI to replace the injectors and find out later that a leak in the intake manifold was causing the surging idle and have to disassemble the TPI again.

I plan on inspecting the EGR and cleaning the IAC while I have it all apart.

Thanks for the replies and I will post if replacing the injectors fixes my problem.

Also,

I need 22 lb injectors, does anyone have an opinion or experience with the pink bosch 22 lb fuel injectors I found on this site below? (opinion about anything other than the color? )


http://www.fiveomotorsport.com/Injector_SetsTPI.asp

 

Waz up theres several tings that cause surgin and you just have to rule em out one at a time start with the things you knows bad and then the cheap fixes like makin a good tool for checkin for vacum leaks and doin a thurogh job of it and then find a freind with a scanner tool make sure all your sensors are good i could go on and on but instead check out my thread on TPI surgin and the hell I went thru and it turned out it was the control module for another guy it was goin to 30lb injectors my point is surge is a common problem that gets uncommonly expensive. Good luck!

 

i've used those pink ford injectors from that site without a problem.