Ignition Retard Problem On 94

[supersleeper]

Hey all,

I've got one of those lousy intermittent problems. Sometimes the car accelerates fast, sometimes the car doesn't want to go faster than 0-60 in three days. I bought a ScanGuage for my ODBII hookup, and when I get acceleration issues it shows the ignition !Removed! as low as -1! When it wants to move, the ignition is arround 19. I have absolutely no error codes. No check engine light. Its driving me crazy. I have noticed strong exhaust fumes and the buildup of black soot on the rear of the car. Any help is much appreciated.

[SKperformance]

With a scanner that shows you ignition timing you should be able to figure it out pretty simply.

If you are looking for directions ,what causes the ignition to !Removed! or not advance?

WHat octane gas do you use?

Always the same gas station?

A/C on?

Does you scanner show you if the knock sensors are being triggered?

Can you monitor the egr flow temp with your scanner?

[Toysrme]

1mz-fe's are notorious for overly sensative knock sensors. They give up 10-15 horsepower from running in limp mode when the knock sensors go crazy. If high octane gas doesn't 100% cure the problem, the only solution is to swap the knock sensors to something else. That project is a completely pain in the !Removed!.

Here's what a '94 1mz-fe (A/T) dyno looks like that's suffereing from over sensative knock sensors. Note how the ECU is pulling timing & trying ot add it back in. Keep in mind this plot was also smoothed. There would be several times as many spikes all over the board if it were not.

For compairison, this 1mz-fe is also suffering from over sensative knock sensors, but not nearly as bad. Dyno smoothing takes out any plot of it also. (But it's still about 5lb-ft / bhp low across the board)

My vote is if 93 octane doesn't fix it, live with it. Even DIY it's going to be a semi-expencive & very, very crappy project to do.

[supersleeper]

With a scanner that shows you ignition timing you should be able to figure it out pretty simply.

If you are looking for directions ,what causes the ignition to !Removed! or not advance?

WHat octane gas do you use?

Always the same gas station?

A/C on?

Does you scanner show you if the knock sensors are being triggered?

Can you monitor the egr flow temp with your scanner?

←

Yeah, I've tried all the usual. Plotting intake temp to octane rating in gas, to octane boosters, to different gas stations. I never run my AC, because the seat of my pants can feel the difference, and I'm an hp hog. I wish it had a knock sensor warning on my ScanGuage, but it doesn't. It is totally random. Often times the loss in hp will last a couple days, then dissapear.

[supersleeper]

1mz-fe's are notorious for overly sensative knock sensors. They give up 10-15 horsepower from running in limp mode when the knock sensors go crazy. If high octane gas doesn't 100% cure the problem, the only solution is to swap the knock sensors to something else. That project is a completely pain in the !Removed!.

Here's what a '94 1mz-fe (A/T) dyno looks like that's suffereing from over sensative knock sensors. Note how the ECU is pulling timing & trying ot add it back in. Keep in mind this plot was also smoothed. There would be several times as many spikes all over the board if it were not.

For compairison, this 1mz-fe is also suffering from over sensative knock sensors, but not nearly as bad. Dyno smoothing takes out any plot of it also. (But it's still about 5lb-ft / bhp low across the board)

My vote is if 93 octane doesn't fix it, live with it. Even DIY it's going to be a semi-expencive & very, very crappy project to do.

←

1mz-fe? I suppose that's the engine model? I wonder what my mechanic would charge me to replace the knock sensor? I used to work on non-computerized engines, but I won't touch these. Too much work. I'm a Network Engineer by trade, and deal enough with computers that I don't want to mix the two. I guess part of that is a lie since I bought a ScanGauge B) , but I do love how much info I get out of it.

It has a full mileage computer coupled with a fault code, realtime customizeble gauges, and it can even deliver commands to the ECU. Not that I would know anything about sending commands, but I would sure love to learn. I know it sends hex codes, and it can save up to 10 preset commands. I wanted to see if there were a way to send a code to disable the knock sensor temporarily and see if it would make the difference in the timing advance.

I read in another forum that the !Removed! in timing is to smooth shift points. Might that reflect some of the drops on the dyno? I havent noticed that random of a power fluctuation, it is fairly linear wheather or not the ignition is retarded or normal. I've observed some light roughness at idle and I have noticed some slight roughness in my transmission shifting. I personally hate automatic transmissions, and never would have bought one on purpose. I don't think that this is the problem I'm having with my ignitio !Removed!.

[SKperformance]

So does your scanner montior the EGR flow temp?

I would bet that is your problem with the car as it is with most.

Give it a good cleaning in the throttle body while you are at it as well.

[Toysrme]

You're right in that tming & shifting is unrelated to your issue.

The moment the TCCU decides to shift a transmission, it retards engine timing to lower output & have less power going throguh the transmission during the shift (softer engagement & less wear)

The timing returns to normal as soon as it's in gear.

Putting new knock sensors in isn't a foolproof way of fixing the problem. You have to do something like swap to GM knock sensors.

[supersleeper]

So does your scanner montior the EGR flow temp?

I would bet that is your problem with the car as it is with most.

Give it a good cleaning in the throttle body while you are at it as well.

←

It does give intake temp, but not EGR temp specifically. I have noticed that EVERY time I take the damn car in for an oil change, they always spill some oil on the engine. Probably the evaporation is cloging up my intake systems. It seems no one can do a clean job or no one bothers to clean up after the spill. I have to run my car with recirculate for the next 2 months.

[supersleeper]

You're right in that tming & shifting is unrelated to your issue.

The moment the TCCU decides to shift a transmission, it retards engine timing to lower output & have less power going throguh the transmission during the shift (softer engagement & less wear)

The timing returns to normal as soon as it's in gear.

Putting new knock sensors in isn't a foolproof way of fixing the problem. You have to do something like swap to GM knock sensors.

←

Interesting. You'd think the dealers would know something about that. I had them take the car for an entire month, and they couldnt fix it! They tried replacing the TPS, but there was no difference at all. I can't really complain, because I got to drive an RX330 for free the entire time! AND they didn't charge me for any engine work ;). I guess you can say that they want my business, but if they can't find the problem...

Thanks to you two, I should have a much better idea next time I take it in. Knock sensors I hear are a common issue, and I know that anything affecting air flow mixture/sensors will cause it also.

One more thing I've noticed while driving. It seems to be consistant per acceleration. i.e. If I acclereate this time, it may be slow and retarded, next time it may be faster and closer to the proper ignition timing. And even sometimes the timing will be dead on. There never seems to be a time where I accelerate, and it is retarded, and then all of a sudden it is dead on. Is that odd or what?

[SKperformance]

Before going off and ventureing into new areas ,look at what i asked you to which is your egr ,then you can start coming to conclusions.

[supersleeper]

Before going off and ventureing into new areas ,look at what i asked you to which is your egr ,then you can start coming to conclusions.

←

I haven't opened the hood since I started this thread. Where on this motor is the EGR valve located? I'm sure its easy to find, I just want to be prepared before I go in...

[Icemaninlv]

i had this problem on my 87 supra turbo.

I had a Check engine light thou for knock sensor and come to find out both knock sensors shared a common ground and one of the sensors positive wires chaffed into that ground causing retarded ignition. I found this with a multimeter and the haynes manual. I ended up eliminating the ground shield and this way the 2 sensors would not touch and this fixed my problem until the oil pump blew but thats a whole other story.

BTW your sensors should be under the lower intake manifold a real pain in the !Removed! but if you plan on changing them I would be worth it to ohm out those wires your an engineer you should be able to fiqure that out.

ICE

[supersleeper]

i had this problem on my 87 supra turbo.

I had a Check engine light thou for knock sensor and come to find out both knock sensors shared a common ground and one of the sensors positive wires chaffed into that ground causing retarded ignition.  I found this with a multimeter and the haynes manual.  I ended up eliminating the ground shield and this way the 2 sensors would not touch and this fixed my problem until the oil pump blew but thats a whole other story.

BTW your sensors should be under the lower intake manifold a real pain in the !Removed! but if you plan on changing them I would be worth it to ohm out those wires your an engineer you should be able to fiqure that out.

ICE

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Yeah, I can, I'm just lazy :D . Too bad the issue isn't consistant enough to give me an error code <_< .

[SKperformance]

The EGR is the rusty pipes by the throttle body with 2 mushroom looking things.

If it gets stuck open you get poor performance but great milage , if stuck closed you get great performance but poor milage.

[supersleeper]

The EGR is the rusty pipes by the throttle body with 2 mushroom looking things.

If it gets stuck open you get poor performance but great milage , if stuck closed you get great performance but poor milage.

←

Rusty pipes?!?! Not on this car B) . Not even on the exhaust manifold! The car has always been garaged, but I think I know what you are refering to. I have removed the filter box and intake mass airflow meter, and everything is super clean inside thanks to my K&N . I don't use the K&N oil with it, only rinse it every so often. Can I tell if the valve is working by testing the vacuum of the tubes? I don't have a vacuum gauge though.