Engine Problems - Toyota Nation Forum : Toyota Car and Truck Forums

MeWantMR2 · 08-30-2007, 08:31 PM

First of all any input on this thread would be very helpful. I have a 91 turbo mr2 with the following problem. If driven at half throttle it runs fine, but if you go into full throttle the engine becomes very uneven and choppy(sputtery). This occurs throughout the RPM band. Has been checked for boost leaks, has none.

Here are a few visible problems.
1. When the engine was hooked up after a clutch replacement some of the emissions control/vacuum lines were removed.
2. The AFM had sealant on the top as if had been removed and replaced.

I have done a little reading, here are my thoughts on the possible sources of the problem:
1. The AFM due to previously mention reason
2. The dealership techs said the timing belts were slipping
3. Malfunction in the boost control system such as the T/VSV.
4. Bad distributor contact
5. Clogged fuel filter.

Please let me know what you think, I really want to drive this car.

Thanks, Ryan

***MR2Jedi*** · 08-30-2007, 11:14 PM

All those scenarios could be the source of the problem.But given that the AFM has been messed with, that would be the 1st thing on my list to check out. No one should ever open them up.If it's been damaged, it will have to be replaced. A used one will do or buy a expensive Engine Management system.

If your timing belt was " slipping", it would already be way off time and you would prolly be smacking a piston top with a valve by now.

The TVIS vacuum valve can be tested. Use the on line BGB sticky in this forum to do so. Check to see that the vacuum line is not breached/leaking/damaged. That valve keeps those flaps open all the way to let in more air at higher RPM's.

I would think that a bad contact in the distributor would show up on a diagnostic without doubt.

A clogged fuel filter could do some of this. Just change it.Especially if it hasn't been changed in a long time. It's inexpensive and simple to do. Then that possiblity will be illiminated

***MRQtwinturbo*** · 08-31-2007, 08:32 AM

replace your ignition components (cap/rotor/wires)...that stuttering could be an exhaust leak also...i had the same problem with mine and had to re-surface the stock manifold....

WT Morgan · 08-31-2007, 05:26 PM

I ditto the cap and rotor as the first approach. It's quick and easy. If that doesn't work, go farther, but those are classic symptoms for a cracked cap or rotor.

MeWantMR2 · 09-01-2007, 02:08 PM

Thnks guys, i'm going to try to replace the rotor and cap and let you know what happens.

Ryan

MeWantMR2 · 09-04-2007, 11:58 AM

Just a thought. From my understanding the distributor is directly related to the engine speed, so if I’m driving and punch the accelerator it starts to shudder instantly, not once the RPMs climb. If the distributor was the problem it would only do this in high RPMs.Let me know what you guy think.

Thanks, Ryan

***MR2Jedi*** · 09-04-2007, 12:32 PM

If you're not getting good spark, you're not gonna get good fuel ignition. RPM,s will not climb very fast or at all if ignition componenbts are that bad.

tHa kNiGHt FaLL · 09-09-2007, 02:02 PM

Quote:

Originally Posted by MeWantMR2

Just a thought. From my understanding the distributor is directly related to the engine speed, so if I’m driving and punch the accelerator it starts to shudder instantly, not once the RPMs climb. If the distributor was the problem it would only do this in high RPMs.Let me know what you guy think.

Thanks, Ryan

the RPM pickup is in your distributor housing. so in that it is directly related to RPM... but if you weren't getting an RPM signal your car wouldn't start.

i would definately lean away from the distributor as your problem.

i'd be checking TPS... Boost Sensor, VAF meter... pretty much the load sensing side of the house that dictates fuel delivery

WT Morgan · 09-10-2007, 09:03 PM

Under acceleration a cracked distributor cap will cause a sputtering/popping/hesitation. It can be strong sometimes and non-existent at other times. It will usually get worse over time. A new cap/rotor costs less than twenty bucks, so it is easy to eliminate as a possibility. The cap could even be tight-wrapped with tape to compress/hold the possible crack as a zero-cost (although not ideal) way to see if it makes a difference and possibly eliminate it as a problem. The rotor is a definate replacement part.

I would still start here and then move forward.

Definately let us know what you find.

MeWantMR2 · 09-12-2007, 11:23 AM

I definately will keep you informed on what happens. Youll have to be patient with me I'm busy with school and work, but i will try to do something soon.

Thanks guys, Ryan

MeWantMR2 · 09-18-2007, 08:51 PM

So I drove the car on saturday and found that the bogging down was not a gradual fade as you step on the gas, but almost instantanious at a certain position it the throttle. My brother said it might br a throttle position sensor. Also the CEL was on, Are there any threads on here that explain how to read the engine code, and a list of what they mean?
Thanks again guys, Ryan