[flyer31]

This is a ’93 LE 2.2 four cylinder. When it is cold it idles and rev’s up great. As soon as it reaches a working temp the engine starts running rough and it’s almost as if it’s only running on three cylinders. When I stop after driving (and jerking) the engine smells like exhaust gas. Sometimes during the drive it is as if the engine has power surges and tends to run fine for a moment or two.
I have done a fair share of trouble shooting but with no success to finding the problem. The following valves and sensors check out fine. TVV, throttle opener, gas filter, idle up valve and EGR valve. I am not sure how to check and test the other vacuum components.

I have used the vacuum diagram found on this site for reference.
http://opc.mr2oc.com/online_parts_catalog/1993_toyota_Vacuum_diagrams.pdf

I would appreciate all and any advice.

Thanks

 

[mustang67408]

This is a ’93 LE 2.2 four cylinder. When it is cold it idles and rev’s up great. As soon as it reaches a working temp the engine starts running rough and it’s almost as if it’s only running on three cylinders. When I stop after driving (and jerking) the engine smells like exhaust gas. Sometimes during the drive it is as if the engine has power surges and tends to run fine for a moment or two.
I have done a fair share of trouble shooting but with no success to finding the problem. The following valves and sensors check out fine. TVV, throttle opener, gas filter, idle up valve and EGR valve. I am not sure how to check and test the other vacuum components.

I have used the vacuum diagram found on this site for reference.
http://opc.mr2oc.com/online_parts_catalog/1993_toyota_Vacuum_diagrams.pdf

I would appreciate all and any advice.

Thanks

Sounds like you have a spark plug or plug wire going bad.
When were they changed last and di you use OEM PARTS?
Is there a check engine light? whats the code?

Coils are also known for going bad on these even if they check out ok.

 

[flyer31]

I replaced the plugs a week ago. No change. I also read some other forums and a couple of people changed the coolant temp sensor with positive results. I tried the same today with no luck. Could it be the ignition coil? If so, where is it located and would it only act up when the engine has come to operating temp? Will it “break down” gradually or does it fail all at once? I am now exploring all options, not just the vacuum system anymore.........

 

[flyer31]

Almost forgot. No "check engine" light

 

[mustang67408]

The coil is inside the distibutor on a 93 4cyl.
Did you change the plugs WIRES as well?

 

[flyer31]

Ok, I put a new coil in. No change. Plug wires are good too. One thing I did was disconnect a vacuum hose where it goes into the pressure regulator (What is the function of the pressure regulator?). The car runs much better but still surges and acts like it has a flat spot or runs on only two cylinders when you accelerate just more than a little. The idling is much better though. With this said could it be the MAP sensor and if so, what are the symptoms of a failing or failed MAP sensor and why does it only happen when the engine is at working temp?
Thanks for the help so far.

 

[mustang67408]

Ok, I put a new coil in. No change. Plug wires are good too. One thing I did was disconnect a vacuum hose where it goes into the pressure regulator (What is the function of the pressure regulator?). The car runs much better but still surges and acts like it has a flat spot or runs on only two cylinders when you accelerate just more than a little. The idling is much better though. With this said could it be the MAP sensor and if so, what are the symptoms of a failing or failed MAP sensor and why does it only happen when the engine is at working temp?
Thanks for the help so far.

The regulator's job is to keep the pressure in the fuel system to a constant 42 psi. It does this with a spring-loaded diaphragm that controls a valve. The valve, when opened by excessive pressure in the fuel lines, uncovers a fuel line that returns excess fuel to the fuel tank.
The vacuum connection is there to help reduce emissions during deceleration. During deceleration, the vacuum connection serves to open the fuel return valve wider, which reduces pressure in the system and prevents excess hydrocarbon emissions due to less fuel being injected as a result of the lower pressure in the system. This is a very nicely designed device in that it provides for an automatic self-adjusting pressure regulator and emissions control device all rolled into one. The simplicity of the design also contributes to its reliability; the fuel pressure regulator rarely, if ever, goes bad. There's just not much to go wrong with it. IT IS BAD IF YOU PULL THE VAC LINE OFF AND THERE IS FUEL COMING OUT OF IT.
When you pull the vaccum line off your actually richening the mixture up.
You could have a vac leak, a bad maf, a bad 02 sensor.
Without a scan tool on it, were just guessing now.
When was the timing belt done? Did it jump a tooth or 2?
A plugged cat converter will act like flat spots, disconnect the exhaust and drive it to see if it gets better. (less restriction)
Without a check engine light I would check fuel pressure first , the ECU does not monitor this and with low pressure you will have driveability problems as you have desrcibed too.

 

[flyer31]

Problem Solved!!!

Thanks for all your help and advice. I checked all the things you mentioned. I thought to check the plug wires again and did so while they were under load. Turns out the #1 wire had a very tiny slit in the tubing on the stem just about an inch above where it plugs into the plus. Somewhere during the course of trouble shooting it went from idling rough when hot to running rough all the time. I re-tested the wires and this time under load and the spark was simply shooting out the side of the wire.

At least I now know and somehow understand the vacuum and electrical on this engine.

Thanks again

 

[mustang67408]

glad to hear you fixed it :tu: