Engine Idle issues

Dnuke · Mar 8, 2020

New to stangnet. Thanks in advance for any help and knowledge I might receive. Been working on my 92 gt (155 k miles) for 1 1/2 weeks now with no accomplishments. Pretty much don't know what to do next. The car will not idle properly. The rpms never go up, just down. And will stall. I can hold the throttle at 2 k rpm and rpms will drop periodically. Getting code 41 and 91. Was getting an egr code but replaced egr and that went away. New O2 sensors. Cleaned maf, new motorcraft iac, new pcv with filter and grommet. New fuel filter, new plugs and wires. Correct voltage on maf and tps. Fuel pressure was 39 psi at schrader valve. Hego wire is connected fine. Did a smoke test to check for vacuum leaks. There was some smoke coming from egr diaphragm, but I read that was normal. And there was a little smoke coming from the top of the tab or tad solenoid (one closest to the fender). No gas leaking out of vacuum port on fpr. Oh yeah and removed kickpanel to check voltage to O2 sensors and that's fine. Can anybody please help? Don't really know what else to do without just throwing money at. Thanks

General karthief · Mar 8, 2020

Any modifications or is it stock?

Dnuke · Mar 8, 2020

Completely stock, and I forgot to mention that it does it if it's cold or hot.

General karthief · Mar 8, 2020

Does your fuel pressure stay steady when it is dying?

Dnuke · Mar 8, 2020

I borrowed a pressure tester from Auto zone to check pressure. That was one of the first things I did. I took it back before reading several posts about it holding pressure. It seems to me like a fuel issue. So I really need to get the tester back and check that.

Dnuke · Mar 12, 2020

Sorry it took me so long to reply. I'll try to make a long story short. I Loaned a fuel pressure tester Monday night. The Ford adapter wouldn't screw on. So I ordered a new schrader valve port. Got it wendsday. Fixed that problem. Put the fuel tester on and had zero on gauge with car running. Took the tester back and went somewhere else to borrow another one. Same result. While the car was running I backed off the Ford adaptor and finally got fuel pressure. The only bad part was it was leaking fuel everywhere. Apparently when you tighten (finger tight) the adaptor down and hook the gauge up it was sealing off the plunger valve inside the Ford adaptor. With both gauges that I rented. One of them being brand new. Anyway did get it to read pressure ( 37 psi) while running ( and leaking) and when the rpms would drop the pressure stayed steady.

Dnuke · Mar 12, 2020

And set timing which was off a little

General karthief · Mar 12, 2020

What is your timing set at now?

Dnuke · Mar 12, 2020

General karthief · Mar 12, 2020

I would replace the egr valve. Then take the vacuum lines off the tab and tad solenoids and plug them. See how it runs then.

Dnuke · Mar 13, 2020

I've replaced the egr valve twice. Smoke tested both times and a little smoke came out of both of them. I will try the tab and tad vac lines

90sickfox · Mar 13, 2020

Take your distributor cap and rotor off. Look down inside and check the condition of the pickup below the window plate the rotor slides on to. It shouldn't be powdery...or crumbly looking.

jrichker · Mar 13, 2020

Dnuke said:
New to stangnet. Thanks in advance for any help and knowledge I might receive. Been working on my 92 gt (155 k miles) for 1 1/2 weeks now with no accomplishments. Pretty much don't know what to do next. The car will not idle properly. The rpms never go up, just down. And will stall. I can hold the throttle at 2 k rpm and rpms will drop periodically. Getting code 41 and 91. Was getting an egr code but replaced egr and that went away. New O2 sensors. Cleaned maf, new motorcraft iac, new pcv with filter and grommet. New fuel filter, new plugs and wires. Correct voltage on maf and tps. Fuel pressure was 39 psi at schrader valve. Hego wire is connected fine. Did a smoke test to check for vacuum leaks. There was some smoke coming from egr diaphragm, but I read that was normal. And there was a little smoke coming from the top of the tab or tad solenoid (one closest to the fender). No gas leaking out of vacuum port on fpr. Oh yeah and removed kickpanel to check voltage to O2 sensors and that's fine. Can anybody please help? Don't really know what else to do without just throwing money at. Thanks

You guys with idle/stall problems could save a lot of time chasing your tails if you would go through the Surging Idle Checklist. Over 50 different people contributed information to it. The first two posts have all the fixes, and steps through the how to find and fix your idle problems without spending a lot of time and money. It includes how to dump the computer codes quickly and simply as one of the first steps. I continue to update it as more people post fixes or ask questions. You can post questions to that sticky and have your name and idle problem recognized. The guys with original problems and fixes get their posts added to the main fix.

It's free, I don't get anything for the use of it except knowing I helped a fellow Mustang enthusiast with his car. At last check, it had more than 250,000 hits, which indicates it does help fix idle problems quickly and inexpensively.

Dnuke · Mar 13, 2020

I plugged the tab and tad vac. lines. Still runs the same. There is no powdery residue in the distributor, just some metal flakes in the bottom. Which I assume is normal. And as for the surging idle checklist, I've basically done everything on it.

General karthief · Mar 13, 2020

You ever replace the distributor?

Dnuke · Mar 13, 2020

No I haven't replaced that, still original

General karthief · Mar 13, 2020

Check it for side to side movement.

Dnuke · Mar 14, 2020

Distributor itself feels solid, the cap moves around a bit. I tried to post a video of my tach while it was running, but it won't download. I also hooked up a vacuum gauge and it reads below normal (13-16 in hg) bounced around in that range.

barry2020 · Mar 14, 2020

I would suggest since I didn't see any mention of it, disconnect the battery! then remove your throttle body and EGR spacer and IAC valve. Thoroughly clean the throttle body with throttle body cleaner, do not use carburetor cleaner. Make sure you clean the throttle plate and EDGES and make sure there is no sticking of the throttle plate and clean the IAC ports too. Do the same with the EGR spacer but only the inside surface going into the intake. For all intensive purposes, instead of trying to clean the IAC valve, especially if its the original, just replace it and the gaskets. Reassemble and do not connect the IAC valve but set idle first on a normal engine temp running engine with the idle adjustment screw. Reconnect the IAC and let the engine run for about 5 minutes with AC off, then if you have it let it run another 5 minutes with AC on. This resets the memory in the CPU. Now set your TPS with a volt/OHM meter with the engine on but not running procedure to < then .98 volts but> then .85 volts. You should be good to go!

Dnuke · Mar 14, 2020

Definitely appreciate all the ideas. I will try anything. The iac is brand new. TB has a sticker on it it to not clean. Is it still ok to clean? I have had it apart when I changed the egr and iac to semi clean the ports ( without cleaner) and put new gasket on then put it back together. Really just want to know if it ok to clean with TB cleaner? Thanks for all the input

Engine Idle issues

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