[OmniEquipped]

My first post here, so hello to everyone. I've been struggling with a drivability problem, so I thought I'd seek counsel from some 5.0 guys.

I seem to be having an issue with my ignition timing. Typically, from a cold start it idles low and is sluggish until it has either reached a certain temperature or has run for a certain amount of time (usually 2 to 5 minutes), then at that point the computer advances the timing and it runs great aside from idling a bit high. It's always done this like clockwork so I learned to live with it, but now it's much worse. It runs different every time I start the engine. The timing rarely, if ever, advances even after reaching operating temp. It idles too low, dies when I put it in gear, and pops back through the intake under a load (strangely it seems to do OK at WOT).

The base timing seems to be adjusted properly. The TPS is adjusted properly.

Any thoughts on this? Is it more likely to be an electronic problem causing erratic computer timing, or perhaps a mechanical issue from the distributor?

[ryanw]

Have you ran codes yet ? Have you checked your fuel pressure and changed your fuel filter ?

[OmniEquipped]

I have checked the fuel and replaced the fuel filter. I don't have a check engine light (I mean I physically don't have one) or a code reader, so I'm working blind in that regard. However, I plan to hook it up to a scanner as soon as I'm able to locate someone who has one. I was hoping there may be a few other things I could check in the mean time.

[ryanw]

you can use a volt test light under the hood at the diagnostic ports to get the codes as well

[OmniEquipped]

Thanks, I may try that. I'm just concerned there will be tons of other codes to filter through due to the lack of emissions components on the engine. This is the reason I didn't wire in a check engine light when I built the vehicle; I figured it would be on constantly.

[ryanw]

DIY KOEO/KOER/Cylinder Balance Self-Test Procedure it shows you many ways to check codes

[OmniEquipped]

I'll give that a shot. Also, do you know off hand which group of sensors may have a direct impact on ignition timing?

[ryanw]

no not really, im guessing the dizzy. that thing thats coming off the Disruptor

[fogged306]

When you're checking/setting your timing are you doing it with the spout connector out?

[OmniEquipped]

Yes, when I set the base timing, it is with the plug out.

[fogged306]

Try leaving the spout out for a couple days and see how the car runs. That way you're eliminating the computers ability to change the timing.

[OmniEquipped]

What I would like to know for diagnostic purposes is which sensor or group of sensors has a direct impact on computer ignition timing?

In terms of the ignition module on the distributor, if it were defective would it cause erratic timing issues or would it just fail and cease to run? Would a defective module trip a code on the computer?

Is the TPS involved with the timing advancement or only involved with the pulse width of the injectors?

[fogged306]

Someone that tunes these cars can answer this better than me, but I can give you a start. The MAF, ECT, TPS, and Distributer itself are the ones I know of. I'm not sure but I think that ACT and the BAP will also have an effect on timing. The computer will change spark tables based on load, RPM, and throttle position as far as I know. The only way to have a good idea if your sensors are functioning is to run your KOEO and KOER codes like ryanw suggested. If you pull the spout and still have the issues, then you know it;s something mechanical in your distributer, or it's your coil or ground connections. If it goes away, then it's computer/sensor related.

[OmniEquipped]

Thanks for the info. So it's basically determined by an accumulation of data. That certainly makes sense. I called a friend this morning who has a Genesis scan tool and he's going to bring it by sometime this week. I think that may be a little easier than using a test light to read the codes considering that there may be a large number of non-related codes due to the lack of emissions components on the engine. In the mean time, I'll try your suggestion of removing the spout. The last time I had it out, everything seemed right as far as the timing staying consistent, which initially led me to believe the issues were electronic, but I need to try it again since the problem has gotten much worse.

You mentioned guys that tune on these...sometimes I wish I had access to someone. There are no speed shops around here, but I actually know a guy here locally who races in the Pro 5.0 class (or at least he did the last time I spoke to him a couple years back) and he's always been really sharp on the diagnostics end of these. But it seems that anytime you have something that's been modified, such as in my case where the engine is in a truck, no one wants to look at it. I guess they think the wiring would be butchered up and hard to work with. However, I used all the OEM components, such as the factory main harness and injector harness. My computer is even located in the passenger kick panel just like a Mustang. It's actually pretty straight-forward and I went to great lengths to make sure it was a nice setup. Worse case scenario, if I can't figure it out I may try to hunt him down and bribe him to look at it.

[mayosailor27]

One thing that can cause probelsm like this (which are close to what I had going on) are bad o2 sensors. I changed many things-- had a bad idle, weird runing, popping, drivability issues and turned out to be old o2's. RUn the codes and keep us updated

[OmniEquipped]

Originally Posted by mayosailor27 One thing that can cause probelsm like this (which are close to what I had going on) are bad o2 sensors. I changed many things-- had a bad idle, weird runing, popping, drivability issues and turned out to be old o2's. RUn the codes and keep us updated

I was hoping to hear if someone had similar issues, so thanks for that information. O2's would be a fairly easy fix, which would be great. When I get it scanned I'll definitely post any results.

[fogged306]

Well your best bet is definitely to run the codes. Just take a pen and paper out with you and write down the flashes as it goes and figure out what they are afterwords. Pulling the spout is a quick check to narrow things down, but if you determine it's on the computer side of things, which it sounds like it probably is, the codes are going to help a lot in narrowing it down.

Edit: .. I was a bit late on that one, hah.

[OmniEquipped]

Thanks for the recommendations so far.

Well, I grew tired of waiting for my friend to bring the scanner, so I decided to brave the arctic weather and headed out with my test light and note pad.

First I ran a KOEO test; the engine was cold. My hands were also cold, so it was difficult to write but I managed, however the ink in my pen was too cold to flow so I just made scratch marks on my pad in a state of disgust. I recorded the following two groups of codes.

First group: 21-23-24-67-81-82-85-95

Separator

Second group: 22-29-41-95

I then ran the engine to operating temp and shut it off before attempting a KOER test. It was a total failure. The engine wouldn't start without applying throttle. The test light stayed on constant for about five minutes, shut off for about 2 minutes, blinked twice and then stayed on constant for about 5 minutes. I tried it three times with nearly the same result.

So based on the codes I recorded from the KOEO test (there are so many), I'm trying to determine my next move. Any suggestions?

[fogged306]

Wow, you've got some codes..

I would think you may have an issue with your vref wire too seeing as how you have a lot of sensor codes that use that vref wire.

Check this page here, it lists all the codes if you haven't found a list of them yet. You may have to sign up to see it, I can't remember how that forum works. KOEO, KOER, CMM and balance test codes 2 digit and 3 digit This is also the same page as the link in ryanw's post but it's the code list instead.

If it were me, I would start by checking all the basics like grounds, including the block to frame and battery to frame, and the EEC to chassis too (another likely suspect with that many codes), the vref and see what the voltage is there. I'm pretty bad with explaining things over the internet and I use some troubleshooting tools that most people don't own, so it's going to be tough for me to help you out much if the problem isn't glaringly obvious from what you find. Joel over at sbftech is pretty good with helping out on electrical issues so he's worth a shot. He's smart and knows his stuff, but just don't take his word for gospel if you do post over there, sometimes there's more ways than one to skin a cat.

With all that going on and the fact that this is a transplant, it's about 99% its a wiring issue. This is a link I posted in that other thread too and it's a lifesaver in situations like these. I rewired my entire harness with that diagram using nothing but a voltmeter and sniffer, which is basically a probe that transmits an FM signal through whatever wire its attached to and has a handheld receiver that pinpoints the wires location throughout the car. It's very useful in tracing wires and finding broken ones. This guy here.

[OmniEquipped]

"Wow, you've got some codes.. " LOL You can say that again.

Thanks for the link to the wire diagram; that's fantastic. I've been using some old black and white papers I printed from Alldata 10 years ago. ryanw's link was instrumental in the code reading procedure, so thanks to him for that.

Ok, so far I've checked the grounds (orange wire at the back of cylinder head, ECM ground strap, and the main battery, engine, frame and chassis grounds). A few years back when trouble shooting the TPS, I was suspect of the VREF wire and I replaced it. It currently shows 5 volts.

After weeding out irrelevant and/or emissions codes from the first group, I'm left with 21-23-24-95.

I think 21 is because the engine was cold? Would a cold engine perhaps also account for 24? (Since there is no place for an ACT on an explorer intake, I have it plumbed in the air intake rubber elbow.) I'm not sure about 23 (TPS). I've got close to .98v or so at closed throttle, but it only shows about 2.5v WOT. I have no idea what code 95 points to.

From the second group (22-29-41-95) I recognize what MAP and HEGO are, but I'm not familiar with the vehicle speed sensor (29) or the fuel pump code (95) again.

What a headache. It's hard for me to find time to stay on it. I would certainly pay someone to get it lined out, but the chances of finding a good tech locally are slim. I guess I'll continue to study the diagram and see if anything comes to me.