Poor running 500 E Odd MAF behavior

[Carl1886]

I’ve been working to get a 500 E that’s been sitting for about 5 years, running again. When I started working on it, the engine was only running on 4 cylinders and found it to be a bad EZL, so I replaced it, and that got it running on all eight cylinders very poorly, so I smoked tested the intake and found it to be leaking from the seals between the upper and lower intake manifold. I replaced those, and no more leaks, but it’s still running poorly.

I noticed the MAF readings were all over the place, ranging from 0 to 50 kg/h at idle, so I replaced it with a tested good MAF, and it still has the same behavior. Any ideas on what it could be?

 

[gsxr]

The MAF readings in your video are not normal. They should be fairly stable. See video below, note that engine is at full operating temp. After a cold start the MAF may read 25-30 kg/hr at idle, but this should drop to around 20 at hot idle.

Your idle RPM is also abnormal. Should be 650rpm in P/N and 500-550rpm in gear.

Has the upper wiring harness been replaced? If not, replace that first. This is what connects to the MAF and could be causing the bizarre readings. If the harness has been replaced, I'd try a spare LH module for grins - can be from any year/model/displacement M119 V8, for test purposes. What was the source of the "good" MAF?

 

[Carl1886]

The MAF readings in your video are not normal. They should be fairly stable. See video below, note that engine is at full operating temp. After a cold start the MAF may read 25-30 kg/hr at idle, but this should drop to around 20 at hot idle.

Your idle RPM is also abnormal. Should be 650rpm in P/N and 500-550rpm in gear.

Has the upper wiring harness been replaced? If not, replace that first. This is what connects to the MAF and could be causing the bizarre readings. If the harness has been replaced, I'd try a spare LH module for grins - can be from any year/model/displacement M119 V8, for test purposes. What was the source of the "good" MAF?

I have not replaced the upper harness but I have measured everything from the MAF back to the ECU and less than 1 ohm on everything. I did see pin 2 on the MAF is CKT 31 or or signal ground (attached diagram) and with the MAF disconnected and the ECU connected (key on or off) I’m reading that pin to chassis ground and it reads open. Could anyone read their MAF pin 2 to chassis ground and see if that’s right. I do have a code in the EA control unit for the gear selector position code 096. Not sure if that code would cause this issue. New MAF sensor came off a running 1993 500 SL.

 

[gsxr]

Check the date on the harness label. Alternately, if there is ANY sign of degraded wire insulation, it's original and MUST be replaced. Easiest locations to check are at the temp sensors at the front of the intake manifold, the cam advance solenoids, and injectors. Good insulation is fully intact and brightly colored. Bad insulation is dull, faded, and will crumble apart exposing a lot of bare copper.

No point troubleshooting further until you determine harness condition. Measuring resistance won't help if the harness insulation is breaking up.

EA code 096 won't affect MAF readings, but could be responsible for the low idle RPM.

Schematics also available here (scroll down to LH-SFI links), but will be tough to read on a tiny phone screen.

Photo of a bad harness:

 

[gsxr]

This is what insulation looks like on a good replacement harness with updated insulation:

 

[Carl1886]

This is what insulation looks like on a good replacement harness with updated insulation:

View attachment 204861 View attachment 204862 View attachment 204863

None of my insulation is cracking I don’t see a date label for the harness though. I do have an extra upper engine harness so I’ll swap it and see if I have any changes. I also ordered an LH from a 1994 500 SL on the eBay.

 

[gsxr]

If the insulation is definitely good, there's no point replacing the harness, but it won't hurt (assuming the extra harness is late datecode). There should be a tag with the harness part number, there are 2 date codes on the tag. Look at FD (manufacture date), ignore ZD (design date). Anything from about 1998 and newer will be a "good" harness with non-biodegradable insulation.

 

[gerryvz]

HOW-TO: Determining the age of your engine wiring harness | "HOW-TO" Tutorial Articles

See attached photos. The manufacturing date of the harness will be on the tag. If the date is 1996 or newer, the harness is not original. The new replacement harnesses made from at least 1998-up (possibly earlier) have improved insulation and do not fail after a few years like the originals did...

www.500eboard.co

 

[Carl1886]

If the insulation is definitely good, there's no point replacing the harness, but it won't hurt (assuming the extra harness is late datecode). There should be a tag with the harness part number, there are 2 date codes on the tag. Look at FD (manufacture date), ignore ZD (design date). Anything from about 1998 and newer will be a "good" harness with non-biodegradable insulation.

View attachment 204877 View attachment 204878

I checked again today and found a date label from 2005. So I guess we’re back to suspecting the LH?

 

[gsxr]

I checked again today and found a date label from 2005. So I guess we’re back to suspecting the LH?

It's a long shot, but I'd try that next for grins. With a good harness and weird readings from 2 different MAF's, I'm not sure what to check next if another LH doesn't help.

 

[Carl1886]

It's a long shot, but I'd try that next for grins. With a good harness and weird readings from 2 different MAF's, I'm not sure what to check next if another LH doesn't help.

I tried a new LH with no luck however, I have discovered if I disconnected the throttle body the readings hold steady.

 

[gsxr]

I tried a new LH with no luck however, I have discovered if I disconnected the throttle body the readings hold steady.

Ahhhhh! Good catch.

What is the datecode on the ETA (Electronic Throttle Actuator), aka throttle body? If original and not rebuilt, that could be causing problems.

 

[Carl1886]

Ahhhhh! Good catch.

What is the datecode on the ETA (Electronic Throttle Actuator), aka throttle body? If original and not rebuilt, that could be causing problems.

This is the only label I see that’s readable. The one on the throttle body is smudged and illegible.

 

[gsxr]

This is the only label I see that’s readable. The one on the throttle body is smudged and illegible.

There's a good chance the ETA is original and may be causing problems due to worn-out internal components. There would generally be fault codes on the E-GAS module, but not always. You can try and find the "triangle" inked date code on the ETA, but that may be illegible as well. See photos at link below.

https://www.500eboard.co/forums/wiki/?title=ETA

 

[Carl1886]

There's a good chance the ETA is original and may be causing problems due to worn-out internal components. There would generally be fault codes on the E-GAS module, but not always. You can try and find the "triangle" inked date code on the ETA, but that may be illegible as well. See photos at link below.

https://www.500eboard.co/forums/wiki/?title=ETA

Tried a rebuild ETA with a date of 2004 still running the same.

 

[gsxr]

What E-GAS module part number is installed? Are there any fault codes present?

 

[Carl1886]

What E-GAS module part number is installed? Are there any fault codes present?

part number 124-545-07-32 there is one fault code in the E gas control unit and it is fault 096 for the starter lockout/shift position

 

[gsxr]

Hmmmm. ok, that's the correct E-GAS for an early 500E. Code 096 is fairly common but should have nothing to do with your problem.

What do the ignition voltages look like on the EZL (EZ1) live data? Also, what is the current status... runs smooth but idle RPM is not steady, or it runs poorly?

 

[Carl1886]

It is running pretty rough. Ignition voltage is staying around 30-32 V. I’ve put 8 GB rebuilt injectors, non resistor Bosch plugs, plug wires, caps and rotors, new Bosch coils, and I’ve tried a spare EZL. Still running rough.

 

[gsxr]

EZL voltages in the low 30's is good / normal. Misfires appear as spikes to 60-70v on the affected cylinders.

Is there any change at full operating temp? How does it drive?

Shot engine mounts can transmit a lot of vibration to the chassis and make it seem like the engine is running rough. If the mounts are old or original, that isn't helping. More info here.

 

[Carl1886]

EZL voltages in the low 30's is good / normal. Misfires appear as spikes to 60-70v on the affected cylinders.

Is there any change at full operating temp? How does it drive?

Shot engine mounts can transmit a lot of vibration to the chassis and make it seem like the engine is running rough. If the mounts are old or original, that isn't helping. More info here.

It definitely has a random miss also backfires on starting. I’m starting to think the timing chain may be suspect.

 

[gsxr]

It definitely has a random miss also backfires on starting. I’m starting to think the timing chain may be suspect.

Hmmm. Something weird is definitely going on. It wouldn't hurt to pull the valve covers and check cam timing on all 4 cams separately.

When the random misfire occurs, do EZL voltages remain steady in low 30's on all cylinders? EZL part number is correct for 5.0L?

Same questions on operating temp and driving...

 

[Carl1886]

Hmmm. Something weird is definitely going on. It wouldn't hurt to pull the valve covers and check cam timing on all 4 cams separately.

When the random misfire occurs, do EZL voltages remain steady in low 30's on all cylinders? EZL part number is correct for 5.0L?

Same questions on operating temp and driving...

Same behavior at operating temp and stumbling in gear and while driving. Voltages remain the same while running and EZL part is correct.

 

[gsxr]

Same behavior at operating temp and stumbling in gear and while driving. Voltages remain the same while running and EZL part is correct.

No change with different MAF and/or MAF disconnected, correct? And no change between cold (driving immediately after a cold start) vs 80C+ operating temp?

Zero fault codes on any modules, except code 096 on E-GAS/EFP?

The car was parked for 5 years... has the gas tank been drained and fresh fuel added? Stale gas can also cause what you describe.

 

[Carl1886]

No change with different MAF and/or MAF disconnected, correct? And no change between cold (driving immediately after a cold start) vs 80C+ operating temp?

Zero fault codes on any modules, except code 096 on E-GAS/EFP?

The car was parked for 5 years... has the gas tank been drained and fresh fuel added? Stale gas can also cause what you describe.

No difference with MAF connected or disconnected behaves the same regardless of temperature I’ve inspected the tank drained it and replaced the fuel filter and put fresh 91 octane non-ethanol. And no codes other than 096.

 

[gsxr]

No difference with MAF connected or disconnected behaves the same regardless of temperature I’ve inspected the tank drained it and replaced the fuel filter and put fresh 91 octane non-ethanol. And no codes other than 096.

If fuel pumps are old/original, it wouldn't hurt to check fuel pressure at the rail while the problem is occurring. I doubt this is the issue but it would be nice to rule it out.

No codes will be stored for issues with fuel delivery, nor most ignition problems, however you have an all-new ignition system and no visible misfires per the EZL live data. I assume you've pulled the insulators behind the rotor bracket to verify there's no liquid on the backside.

Running out of ideas here...

 

[Carl1886]

If fuel pumps are old/original, it wouldn't hurt to check fuel pressure at the rail while the problem is occurring. I doubt this is the issue but it would be nice to rule it out.

No codes will be stored for issues with fuel delivery, nor most ignition problems, however you have an all-new ignition system and no visible misfires per the EZL live data. I assume you've pulled the insulators behind the rotor bracket to verify there's no liquid on the backside.

Running out of ideas here...

Yeah, likewise, I’m kind of running out of steam on this one. I replaced the insulators behind the rotor and the seal around the cam. There was no liquid behind it when I was inspecting. I also checked the fuel pressure and delivery and everything was in spec.

 

[gsxr]

Have you watched fuel pressure while the problem / misfire / etc is occurring? If so, that rules out an intermittent fuel delivery issue, assuming the gauge showed 45-55psi.

Less likely is a defective new ignition component... more than one forum member (myself included) have encountered defective new parts out of the box. However, a misfire will always appear as a spike in ignition voltage on live data for the affected cylinder. If you never see voltage spikes, it's unlikely that secondary ignition is the cause.

Next up is a smoke test along with chasing every single vacuum pipe. Top of the list is the 8mm plastic pipe from the PCV hoses on top of the intake manifold, which goes to the purge (MOT) valve by the EZL. If the purge valve is stuck open this will cause a large vacuum leak. You can temporarily disconnect / plug the fitting at the manifold for testing. I assume since you swapped ETA's that the large hoses to the passenger valve cover are all good and connected properly.

 

[Carl1886]

Have you watched fuel pressure while the problem / misfire / etc is occurring? If so, that rules out an intermittent fuel delivery issue, assuming the gauge showed 45-55psi.

Less likely is a defective new ignition component... more than one forum member (myself included) have encountered defective new parts out of the box. However, a misfire will always appear as a spike in ignition voltage on live data for the affected cylinder. If you never see voltage spikes, it's unlikely that secondary ignition is the cause.

Next up is a smoke test along with chasing every single vacuum pipe. Top of the list is the 8mm plastic pipe from the PCV hoses on top of the intake manifold, which goes to the purge (MOT) valve by the EZL. If the purge valve is stuck open this will cause a large vacuum leak. You can temporarily disconnect / plug the fitting at the manifold for testing. I assume since you swapped ETA's that the large hoses to the passenger valve cover are all good and connected properly.

I have smoke tested the intake and I had a little bit of smoke come out of the EGR valve however, I think this is normal behavior. I’ve also tried disconnecting and plugging the purge line to see if there’s an issue with that with no change

 

[nocfn]

as a note, it took a while before the smoke pressure built up in the manifold before it made its way out of the EGR gasket on my car.

 

[gsxr]

I have smoke tested the intake and I had a little bit of smoke come out of the EGR valve however, I think this is normal behavior.

Yeah, I wouldn't worry about this. You can test the valve itself with the engine idling. Apply vacuum to open the valve, the idle should become rough when vacuum is applied to the valve, and smooth out when vacuum is removed.

I’ve also tried disconnecting and plugging the purge line to see if there’s an issue with that with no change

Good - one more suspect eliminated. Double-check the purge valve anyway, make sure it's not leaking. It should be 100% closed unless voltage is applied to open the valve.