Helping my son with his new (to us) 86 TA, TPI 305, auto trans. Does not seem to have any mods.

Problem: high idle (1,000 to 1,200), remains open loop, EGR shows as "ON" although ECM is requesting 0% duty cycle. O2 sensor showing no action and hovers around 200 to 300 or so. No codes.

He did have peices of the cat comming out of the exhaust and did a roto-router job until the new one goes in, but I don't want to install the new cat until the engine is running properly.

Son complains engine has no power over 3,000 RPM and sometimes hesitates and breaks up. This still after the cat "fix".

Scanner is an Auto X-Ray, I was told this may provide bad info on an 86 ecm, but reading posts here I did not see any complaints about this unit.

Any thoughts on this before I start taking it one sensor at a time?

Thanks Guys! BTW, great board you have here.

Pete

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1989 Corvette L-98 Bright Red FX3 Z51 Coupe
Michelin MXX3 285/40 17
B&B Tri-Flows, Cyro Tempered rotors, Praise Dyno Stage II pads

 

hello, i don't know anything about your scan tool, but i know the 85-87 5.0 & 5.7 tpi veh. need a special adapter for the GM tech 1 to read data...believe me, i have a 86 iroc and spent many day's trying to figure out why my data was so screwed up.(and i work at the dealership). for some reason, the tpi's data to the aldl connector is on a different wire. hope it helps, let me know if you need anymore help, best of luck, tom

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86 iroc 305tpi auto. mild cam

 

Thanks Tom. I'll try and put in diagnostic mode this weekend and see if the SES light will blink to show open vs. closed loop. This should tell me if the scanner is talking to it correctly - at least for that parameter.

I was getting readings such as TPS and all, and they seemed to be about right, so it's talking - just not sure if it's correct.

If anybody can think of anything else, it would be great.

Pete

 

Not claiming to be an auto mech. by any means, however I have the same engine as your son- just in a different body ('86 IROC-Z) My car has had the same problems...My car wouldn't go into closed loop mode- The way it was fixed was simply with a O2 sensor replacement...as for the idle mine was corrected by proper adjustment of the TPS and IAC motor/sensor, not to mention the vacume hose to the EGR (or was is it the PCV??)was wasted causing a higher idle. Keep in mind a vacume leak could also cause a higher idle. My high idle problem is back though- only worse this time (1,500 - 2,000 RPMs) I can't solve this with a mere adjustment, but I presume faulty IAC. The IAC is located and attached to directly underneath the throttle body. In my Hayes® manual is describes simply cleaning the blades with carb cleaner and wiping them off with a lint free towel (accessible by removing the flexible oval rubber duct from the front of the throttle body). It also mentions removing the IAC and cleaning it's passage loacated in the throttle body with carb cleaner. This procedure is to determine if you need to go a step further by adjusting the TPS and "minimum air". For me to do this, I had to remove the entire throttle body (get the gasket if need be first) to access the IAC. When the IAC is removed, starting from the end of the "O" ring to the tip of the pendle should measure no longer than 1 1/8". Let me know if you have tried to set the "minimum idle" on the car yet. It has to be done a certain, and the instructions in this site aren't detailed enough- let me know if you would like this procedure according to my Hayes® manual.

 

Thanks Roc! I'll let you know how it works out.

Same TB / IAC / TPS as my vette and I've done the job before. Figured that's what it was. Know the proceedure well!

I'll do the O2 first to see if it will go closed loop. Then pull the TB and clean. Think I'll replace the IAC, what the heck. Then setup the minimum idle and TPS.

If all that works then trace the EGR. Confused why this is not setting a code, but one thing at a time. Could be it will when the engine goes closed loop.

Thanks, just needed a direction check.

Pete