DaveGlasscoc

Hi and thanks in advance for any help you can offer. I've been working on my own vehicles, including two mustang 5.0s for most of 30 years but I am stumped on this problem.

I have a 94 GT convertible that won't idle anything close to smoothly unless I pull the SPOUT. I have codes: KOEO 654 and 564 and KOER 536 and 632 none of which relate to any sensors and are pretty much what I expect with the car in neutral and not tapping the brake pedal.

The car starts fine but quickly idles down under 1000. Then it will drop 1-200 rpm with some drops down to 500 rpm. At 1000 rpm the car vibrates terribly, but that may be unrelated. If I pull the SPOUT the car idles fairly smoothly around 800 rpm and drives just fine. If I drive with the spout in the car pings like crazy. I get that the ECM is advancing the timing incorrectly but I have no idea at this point why or what sensor is causing it.

I have changed the following parts in the three years I have had the car and it is not operated daily but is a project car for me and my son to work on and my wife to drive. ;-)
Items with * I changed after I began to experience the issue
EGR Valve and position sensor
O2 sensors- both
*TPS
*IAC
*Temperature sensor
Distributor
Plugs
Wires
Cap and rotor
*MAF (BBK)
*TB (BBK)
*Ignition module
* ECM
*PCV valve
I've also pulled the plenum and replaced the brittle old vacuum hoses.

The problem started only after it warmed up and was not under load. I adjusted the timing (SPOUT out), which was very advanced (not on purpose) to 10* but that didn't help any. Over time the problem got progressively worse to where it is now.

Any suggestions would be greatly appreciated! My next step is to take it to a mechanic but I would hate to have to do that, especially after putting as much effort as I have into it.

Unrelated, I believe, parts I have changed:
Water pump, thermostat, radiator, hoses, heater hoses, air conditioner compressor and clutch, a/c hoses, condenser (basically all a/c and cooling under the hood), all the under car stuff, brakes, shocks, etc.

++++++++++++++++++++++The 5.0s I've owned+++++++++++++
1994 Red GT Convertible
1982 Blackout GT Hatchback
1978 Granada - Now that's fancy!
1973 Torino - not like Starsky and Hutch's!

88 orangepeel notch

Find TDC on #1 cylinder, on compression stroke. Verify outer ring on balancer hasn't moved.

Oh, and welcome to the forum. Hopefully we can help you get this sorted out.

jwog666

^^^^^^^^^^^^^^^^^this. its common, and if it has slipped you may be very advanced with spout in

DaveGlasscoc

Thanks guys! I will probably just replace the balancer to be sure, in the next day or so, and let you know how it goes.

DaveGlasscoc

Update - That did the trick! I ended up replacing the balancer, the timing cover was cracked so that went too. While i was in there I replaced the timing chain set and the oil pressure switch since they were easily accessible. After reassembling and resetting the timing, it runs smoothly with zero pinging with SPOUT in. Perfect!

Thanks again for the advice!

88 orangepeel notch

That's great, glad we could help.

DaveGlasscoc

Ok, so I thought everything was fixed but, as it turns out, a problem I thought was related to the timing issue appears not to be. When cold the car runs great. No pinging under load, smooth acceleration, perfect. After about 10 to 15 minutes of operation, however, I experience intermittent hesitation under light load and, if I run WOT, it pings again pretty heavily but the hestitation disappears. If I cruise at idle, all is well.

I had some plug wires of questionable quality so I changed those out along with the plugs but the issue persists.

Any suggestions? This has been going on for some time and adjusting the timing was one of the things I did to "fix" it that landed me in the situation outlined in the original post. All the things I replaced to try to correct it are outlined there.

88 orangepeel notch

I'd pull codes to see if there are any stored, that may help point us in the correct direction.

So somehow it's advancing timing when warm ? Hmmmm,. If your dizzy is locked down at 10', only the ECM could do that. Does your car have an aftermarket chip ? One of those plug and play tunes ?

jwog666

its possible that the timing chain is loose or has jumped, this will cause these concerns as well. some of those timing sets had a nylon coated gear that was prone to wear and getting very loose

DaveGlasscoc

Thanks for the responses. I will pull codes when I get home this weekend. I should have done that already, in hindsight.

The ECM did have a chip in it but I replaced the whole unit without the chip when trying to fix the idling issues so it is back to stock.

I just replaced the timing chain when I replaced the harmonic balancer and timing cover so I don't think that will be the problem.