Good afternoon all. My car, a 1997 Toyota Corolla has developed a problem I’m hoping maybe someone can help me figure out.
Lately I’ve had a plethora of work done to the car. I’ve had the gas tank, fuel pump, all four struts, main oil seal, plugs, wires, cap, rotor, transmission fluid/filter, motor oil/filter etc, all replaced. The car actually runs pretty good, except, after having the main oil crankshaft oil seal replaced, the car has developed a problem.
It feels like I got bad gas but I don’t think that’s the problem. If I press too hard on the accelerator, the car wants to stall. If I take things nice and easy, and ease off the accelerator right as the car goes to shift, it’s fine, but if I want to pass someone and try and kick the car into the passing gear, it wants to stall. If I ease off the gas it’ll correct itself but I still can’t accelerate quickly. The check engine light does NOT come on, nor did a mechanic get any error codes when he plugged up his computer to it.
Like I said this didn’t start happening until after the main oil seal was replaced so I’m wondering if the mechanic messed up something. Would anyone know what might be causing this problem? Thanks for your time.
Have someone check the signal out of the MAP sensor.
MAP Malfunction
All fuel-injected Jeeps use a MAP (manifold absolute pressure) sensor to determine how much fuel the engine requires. The MAP sensor monitors engine manifold vacuum and translates that reading into an electric signal sent to the ECU. Depending on the voltage from the MAP sensor, the ECU will fire the injector for a longer or shorter burst to deliver more or less fuel, as the case may be. It’s a fairly foolproof and simple design, but they can have issues. If after the engine has come up to operating temperature your Jeep suffers poor drivability, surging, rough idle, excessively rich exhaust, or pinging even with mid-grade fuel, chances are the MAP sensor has begun to go out of range or has failed altogether. The thing is, a bad MAP sensor won’t always trigger a check engine light or cause the computer to register a DTC (diagnostic trouble code)
Good ideas above. Another possibility , the hesitation on rapid acceleration could be an EGR system malfunction, most likely related to the throttle position sensor. The EGR valve is supposed to open wider on gradual acceleration to prevent the engine’s internal parts from overheating, and to minimize air pollutants. But not on very rapid acceleration. That’s b/c rapid acceleration means the driver may be attempting to pass, and needs all the engine power available for safety. On my own Corolla (early 90’s), that’s done w/the throttle position sensor. When the computer senses wide open throttle, it automatically disables (closes) the EGR valve.
Thre are two crankshaft oil seals, one in the front of the engine, and one at the back. The back one is much more difficult to replace b/c the transmission is in the way. Do you know which one? If it was the back, lots of stuff has to be disconnected, and quite likely the tech forgot to re-connect the sensor when putting it all together again. If so, there may be other sensors disconnected as well.
It’s quite easy – at least on my Corolla – for a shop to disable the EGR system completely as a test of this idea. Don’t drive long distances like that, test purposes only , could cause engine damage.
It was the crankshaft seal on the front of the engine that was replaced. I’m taking the car back to the shop Tuesday to have the battery, battery cables and air filter replaced. Should I have them check out the MAP and EGR valve? The suggestion above said the MAP won’t always trigger a check engine light, would the same thing go for the EGR valve? Also, would either of these two items be something that perhaps had to be unplugged or removed to get the oil seal replaced? Thanks for your help.
Could the MAP have been damaged in some way when the oil seal was replaced? In other words, might the mechanic have done something to it, that though it is plugged in, that could have caused it to malfunction?
It’s easy to check the MAP sensor’s basic function b/c it should read atmospheric pressure with the engine off, appx 15 psi. So yes on that one. Ask them to also verify the MAP sensor is correctly attached to the intake manifold. If that hose came off it would create a big vacuum leak, and this symptom could result. Usually it would show up immediately as a poor idle though .
Some EGR problems will turn on the CEL light if the valve itself fails, but some won’t. At least on my own Corolla the computer measures the EGR’s temperature, to verify it is open when it should be. But it doesn’t have a way to verify the throttle position sensor is working. The computer uses throttle position sensor to know when to close the EGR valve. I think the best course is to presume the EGR valve is working ok, and your shop should test the throttle position sensor, which they can do with their scan tool at the same time they test the basic function of the MAP sensor.
More likely a ground connection was inadvertently left disconnected. I’d have to disconnect the cylinder head to chassis ground in order to get access to do that job on my Corolla.
I just came from the shop and they still can’t figure out the problem. I think I’m going to have to take it to a Toyota dealership and see if they can look at it. I’m at my wits end and apparently these guys did something to cause the problem that they now can’t diagnose.
Frustrating! I presume the suggested tests above have been done w/ no clear cause found. Suggest to keep us up to date on the progress. Since the problem showed up immediately after the front crank seal was replaced, most likely has something to do that. I’ve never done it myself, but I believe the job requires removing the crankshaft pulley and timing belt cog. hmmm… besides the ideas above, it’s possible the timing belt was re-installed on the cog incorrectly, yielding incorrect valve timing. That would definitely create weird and hard to diagnose symptoms.
I don’t know where the crank sensor is on this but on my Buick it was around the balancer which would have been removed for a front seal. A bad crank sensor gave me a hesitation on heavy throttle, until it didn’t and stalled.
Forgive me if everything doesn’t come back in chronological order anymore. Had another crank sensor that just quit with no symptoms.
The timing belt and the timing was something the mechanic said he was going to check on, but he can’t work me in until the end of next week. So I’m going to drop in on a local Toyota repair shop tomorrow and see what they can tell me. I dread going there but I don’t know that I have any other choice at this juncture. I’ll keep you up to date!
I wonder about that sensor as well. I’m pretty convinced that this problem has something to do with whatever he did to change that crankshaft seal, and if that sensor is faulty and/or can cause this issue, then I need to get it replaced before I find myself out in the middle of nowhere with a car that won’t run. I’ll keep you all up to date!
My Corolla is an earlier model year (92), so this may not apply to yours, but it is pretty easy on mine to verify the valve timing is correct .15- 20 minute job. On mine the crank sensor is in the distributor, not anywhere near the crankshaft seal.
I’ve heard putting the timing belt on off one notch is a common mistake. The result is usually poor gas milage and performance and nobody knows why.
The Camry has a crank sensor under the timing belt cover, and another sensor in the distributor. If there is significant mismatch it will trigger the MIL. I assume a Corolla is similar.
Have you tried putting it is 2nd gear to get the engine up near 5000 RPM and then increasing the throttle to see when it starts to misfire? Does it happen immediately? Does it misfire but start to get better if you hold the throttle in the same place? Do you overall have less power when in 2nd gear? That could be a fuel starvation issue.
The car should still run with the MAP or TPS unplugged. You could try that for a bit to see if there is a difference.
EGR is most active at low throttle or high vacuum. When there is little vacuum in the manifold EGR circulation will be low. In fact, I believe the EGR VSV is supposed to turn the system off completely at full throttle.
An engine that is running too lean usually make a bit of a hot burning smell.
Someone can monitor the oxygen sensor Voltage while you’re driving to see when it starts to run too lean or rich.
