87 Mustang 5 speed running really rich hard start when warm....

Topic: 87 Mustang 5 speed running really rich hard start when warm.... (Read 9282 times) previous topic - next topic

87 Mustang 5 speed running really rich hard start when warm....

Reply #15 – December 04, 2013, 01:58:21 PM

Quote from: 88turbo;425221

Paul, Check the TPS for broken wires.

TPS is good. No flat spots .8v or so at KOEO on the idle screw stop and sweeps to 4.5v in the WOT position.

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It is a possibility even without a code. The computer throws a code when a sensor is out of range. If it fails to read properly but is in range.....no code. I just fixed an issue similar to this on my son's 89 Daytona. Modern cars are a bit smarter, but they still lie, too.

There's an old thread in here in where I basically confirm that with the HEGO system. I had a custom exhaust fabricated and long story short My o2 sensor harness had been swapped to read the wrong banks. No codes whatsoever..... Found it: http://www.foxtbirdcougarforums.com/showthread.php?21560-White-10-pin-connector

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check the timing. maybe someone swapped a cam in and set it too far advanced or retarded, or dropped the dist in wrong. could be firing all the injectors to the wrong cylinders.

Timing's @ 12, spout's connected, stock cam, distributor is installed correctly. Checked all this previously.

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He did cap off the line to the manifold when he removed the charcoal cannister?

ZERO VACUUM LEAKS.

This is yet another reason why I prefer finding a T-Bird or Cougar over a Mustang. They're usually stock or near it and those who DO modify them are a smaller community -- hell, most everyone I've ever met with a modified Cat or Bird is aware of this site!

If I ever purchase a fox Mustang myself, you can bet your ass I'll shop around for one who's owner had a clue and not some kid who hacks things to pieces..... I see them go for top dollar hacked up and running like garbage....

87 Mustang 5 speed running really rich hard start when warm....

Reply #16 – December 04, 2013, 04:13:57 PM

Sounds like you guys are on it pretty well. At this point I'm guessing it's either a weird sensor IAT, CLT, or MAP, or the EEC computer is Tango Uniform. You are SURE the computer ground is good. (I'm sure you checked it.)

87 Mustang 5 speed running really rich hard start when warm....

Reply #17 – December 04, 2013, 04:15:44 PM

Quote from: Dougy_Fresh;425213

i'd start with checking all the sensors, mainly the coolant temp sensor, intake air temp sensor, and map sensor

I'd check the coolant temp sensor. It acts like a choke to enrich the mixture on a cold start. If it's acting up the engine will run rich all the time. You said that on a cold start it runs fine. That points in the direction of the coolant temp sensor.

Quote from: V8Demon;425231

TPS is good. This is yet another reason why I prefer finding a T-Bird or Cougar over a Mustang. They're usually stock or near it and those who DO modify them are a smaller community -- hell, most everyone I've ever met with a modified Cat or Bird is aware of this site!

If I ever purchase a fox Mustang myself, you can bet your ass I'll shop around for one who's owner had a clue and not some kid who hacks things to pieces..... I see them go for top dollar hacked up and running like garbage....

That's kind of why I bought a Mark VII. The engine and wiring was stock. At least I know if modifications get done they will be done correctly and not hacked. You won't believe the things I've seen on 5.0 Mustangs. Plus any Mustang with a BBK "cold air" kit and headers/exhaust is "modded and fast" therefore worth the $5K the guys is asking. Sure.

87 Mustang 5 speed running really rich hard start when warm....

Reply #18 – December 04, 2013, 08:40:35 PM

http://forums.corral.net/forums/5-0-5-8-engine-tech/303906-5-0-hard-no-start-when-hot.html

http://forums.corral.net/forums/5-0-5-8-engine-tech/845445-hard-starting-hot.html

Me thinks the ECU has taken a dump?

Darren

87 Mustang 5 speed running really rich hard start when warm....

Reply #19 – December 04, 2013, 09:27:59 PM

To be honest, that's what I'm leaning towards at this point too....

Anyone got a DA1 laying around?

87 Mustang 5 speed running really rich hard start when warm....

Reply #20 – December 04, 2013, 09:53:58 PM

I don't have a DA1, but I have the equivalent from a Mark 7, if you need one simply to verify the EEC is (or isn't, whichever) is good.

Let me know...I can send it your way in the AM, Paul.

87 Mustang 5 speed running really rich hard start when warm....

Reply #21 – December 05, 2013, 08:51:40 AM

I'll take it. Shoot me a PM. I'll pay for it and the guy will pay me back. He lives a few blocks away from me so I know he aint going anywhere, lol.

87 Mustang 5 speed running really rich hard start when warm....

Reply #22 – December 05, 2013, 07:25:43 PM

If that dont go through, i have a Da1 i will sell you. Came out my bird before i switched to mass air.

87 Mustang 5 speed running really rich hard start when warm....

Reply #23 – December 13, 2013, 02:25:46 PM

My $.02 based on two experiences of rich running Turbo Coupes: It was the FPL which read fine at idle but was dumping in massive fuel when driving. You would need to tape fuel pressure gauge to the windshield and drive it to check. If you know it is rich at idle, then this is not it as you checked FP.

What tells you it is rich? The smell? Exhaust color?

Also, if O2 sensors detect false air like from an exhaust manifold leak, they will try to enrich the mixture.

87 Mustang 5 speed running really rich hard start when warm....

Reply #24 – December 13, 2013, 02:37:37 PM

Quote from: kuchak;425578

My $.02 based on two experiences of rich running Turbo Coupes: It was the FPL which read fine at idle but was dumping in massive fuel when driving. You would need to tape fuel pressure gauge to the windshield and drive it to check. If you know it is rich at idle, then this is not it as you checked FP.

What tells you it is rich? The smell? Exhaust color?

Also, if O2 sensors detect false air like from an exhaust manifold leak, they will try to enrich the mixture.

Sorry, I meant FPR, fuel pressure regulator, not FPL.

87 Mustang 5 speed running really rich hard start when warm....

Reply #25 – December 15, 2013, 12:51:41 PM

Have you had time to see if the ECC was the issue?

Darren

87 Mustang 5 speed running really rich hard start when warm....

Reply #26 – December 15, 2013, 10:28:26 PM

I'm curious on this as well.

87 Mustang 5 speed running really rich hard start when warm....

Reply #27 – December 16, 2013, 11:02:06 AM

Late to the party but my guess is if it will give expected codes for induced faults the ECM is probably OK...

What I'd do is disconnect both o2 and run it, if the problem changes then maybe a heater is shorted internally causing issues... If that didn't help, disconnect every sensor other than TPS & MAP, the engine will still function reasonably well on only these sensors... If that doesn't do it then wiring or maybe the ECM...

Of course if fuel pressure is high A/F will be extremely rich...

Any chance it has the wrong ECM installed???

87 Mustang 5 speed running really rich hard start when warm....

Reply #28 – December 21, 2013, 07:06:49 PM

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What I'd do is disconnect both o2 and run it, if the problem changes then maybe a heater is shorted internally causing issues

Had him do that early on. No change whether hooked up or disconnected.....

Update: He was able to borrow a known good DA1 ECU and swap it in....... No change.....

87 Mustang 5 speed running really rich hard start when warm....

Reply #29 – December 21, 2013, 09:33:35 PM

Unless I misunderstand the function of O2 sensors entirely, I believe they are "fine tuning" in a sense. They exist as feedback and thus can't cause an engine's A/F ratio to go *drastically* rich or lean. I'd bank on the ECT, ACT or MAP.

When it's warmed up, does it start better if the throttle is opened any amount?