1.8 Shudders Under Load Only

[JasoninBRLA]

With clutch in or not in gear I can redline it no problem with no missing. 0 to 60 in 30 seconds otherwise it shudders like I'm driving down train track. CEL will blink while shuddering then quit. Then CEL stay on and give me a random 1 of the 4 cylinder missfire.

Guys any ideas. I'm lost.

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[krazeedrivr]

It could be a bad abs wheel speed sensor (or 2). One of mine is going out and it does that exact same thing when I turn around sharp corners. It could definitely also be your engine harness shorting out. I'd start with investigating the wiring to your ignition coils. I had to splice in 4 new ignition coil pigtails on mine for same issue.

[egovreau]

Check your spark plugs first. If they're worn out or gapped incorrectly (too large vs to small) then that's a likely cause.

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[JasoninBRLA]

Rebuilt top half 6 months ago with new plugs. Been running fine up until recently.

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[JasoninBRLA]

Could wheel speed sensor impact how the motor runs?

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[Dfraney]

With clutch in or not in gear I can redline it no problem with no missing. 0 to 60 in 30 seconds otherwise it shudders like I'm driving down train track. CEL will blink while shuddering then quit. Then CEL stay on and give me a random 1 of the 4 cylinder missfire.

Guys any ideas. I'm lost.

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General rule of thumb/process for misfires:

1) Swap coils (either swap the cylinders that are missing with ones that aren’t or just throw a new set in)
2) Inspect coil pack wire harness, these are known to crack and fray
3) Inspect spark plugs for corrosion, hot spots, carbon build up, and check gap as well if tuned
4) Inspect injectors if above mentioned failed to isolate issue, swap same as coil packs

If all else check outs, you may have an issue elsewhere either being a vacuum leak or faulty MAF, MAP, TB, boost leak, etc.

[krazeedrivr]

Could wheel speed sensor impact how the motor runs?

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Absolutely. Bad wheel speed sensors can make the ECU think you have wheel spin and the ESP throttles the motor like you are describing. The misfires are either coincidental(trying to throttle the motor under load), or as I said electronic in nature. Being that you are having random misfires, I don't see it being coils or plugs, rather the OLD wiring we are all dealing with at this age. Try turning off ESP and see if it resolves the issue. If not, follow the troubleshooting we have described above.

[Mike Tries]

It's pretty easy to check the ignition wiring. Maybe 10 minutes or so worth of work. Pull your engine cover off, pick a coil, and pull back the rubber boot thingy until you can see the wires under it. If you look in there and see four copper wires with no insulation getting real friendly with each other, you'll know your wiring is fried. You should check all four connections, but if you find a failed one, then you should just go replace the harness. It's not as big of a job as it sounds. The absolute worst part of the job was getting the dang windshield wiper off to get to that ONE screw holding the ECU cover on.

If you're feeling brave, go ahead and check the wiring where it plugs into your fuel injectors (I've not been so brave yet). You might be in for a surprise there, too, but it doesn't sound like the cause of this particular issue for you right now.

I'll echo what others have said about the plugs... double-check the gap. But do the easiest stuff first--it's really easy to look at the wires under the boots.

[Kevin C]

Could wheel speed sensor impact how the motor runs?

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I know on my car when the traction control kicks in you will see a flashing light on the dash letting you know it activated.

[walky_talky20]

This sounds like a textbook 1.8T weak ignition coil situation. The 1.8T ignition coils are very high failure rate. All of them get weaker over time as the secondary winding degrades. You will almost always notice the weak spark in boost/hard acceleration first (if you drive it hard, anyway). Extreme temperatures can also worsen the symptoms.

You can try to figure out which one(s) are weak by lifting the coil off the plug gradually while the engine is idling (carefully, at your own risk). By doing this you can determine which coil causes a cylinder to drop-out with the least amount of lifting. You are forcing the coil to generate higher voltages to jump the additional gap between the coil and plug. If the coil is very weak, you will not be able to lift it very far or at all.

The coil-lift test is pretty easy, but there exists a special (and cheap) tool to measure the attainable coil output voltage more "scientifically": https://www.lislecorp.com/specialty-...g-spark-tester

Or you can just throw 4 new coils in it. ;) Good Luck.

The wiring harness concerns are definitely valid, and you should inspect that - but I find harness issues to be much more rare than your standard weak ignition coil issue. Especially if its only cutting out under load.

[AvantNoir]

Definitely sounds like wire issue

[JasoninBRLA]

General rule of thumb/process for misfires:

1) Swap coils (either swap the cylinders that are missing with ones that aren’t or just throw a new set in)
2) Inspect coil pack wire harness, these are known to crack and fray
3) Inspect spark plugs for corrosion, hot spots, carbon build up, and check gap as well if tuned
4) Inspect injectors if above mentioned failed to isolate issue, swap same as coil packs

If all else check outs, you may have an issue elsewhere either being a vacuum leak or faulty MAF, MAP, TB, boost leak, etc.

Definitely not 1-3. I will check 4 this weekend.

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[JasoninBRLA]

Absolutely. Bad wheel speed sensors can make the ECU think you have wheel spin and the ESP throttles the motor like you are describing. The misfires are either coincidental(trying to throttle the motor under load), or as I said electronic in nature. Being that you are having random misfires, I don't see it being coils or plugs, rather the OLD wiring we are all dealing with at this age. Try turning off ESP and see if it resolves the issue. If not, follow the troubleshooting we have described above.

I will try this Saturday.

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[JasoninBRLA]

This sounds like a textbook 1.8T weak ignition coil situation. The 1.8T ignition coils are very high failure rate. All of them get weaker over time as the secondary winding degrades. You will almost always notice the weak spark in boost/hard acceleration first (if you drive it hard, anyway). Extreme temperatures can also worsen the symptoms.

You can try to figure out which one(s) are weak by lifting the coil off the plug gradually while the engine is idling (carefully, at your own risk). By doing this you can determine which coil causes a cylinder to drop-out with the least amount of lifting. You are forcing the coil to generate higher voltages to jump the additional gap between the coil and plug. If the coil is very weak, you will not be able to lift it very far or at all.

The coil-lift test is pretty easy, but there exists a special (and cheap) tool to measure the attainable coil output voltage more "scientifically": https://www.lislecorp.com/specialty-...g-spark-tester

Or you can just throw 4 new coils in it. ;) Good Luck.

The wiring harness concerns are definitely valid, and you should inspect that - but I find harness issues to be much more rare than your standard weak ignition coil issue. Especially if its only cutting out under load.

I've had the car 17 years and changed out several bad coils. This is different. Also when I replaced the head gasket I replaced every hose and changed out all brittle and suspect electrical plugs. Especially the ignition wiring which was really really bad.

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[JasoninBRLA]

Guys. I appreciate your efforts and will keep you updated on my progress. I love this car and plan on driving it till I die.

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[walky_talky20]

Have you checked your plugs and boots for carbon tracking? That can definitely cause a misfire that isn't quite the same as a weak coil or a worn plug. It sparks right down the side and skips the spark plug electrodes altogether.