86 corolla run's very rough and burn's lots of fuel
It started last year. Sometimes after a few minutes on the highway i'd notice that my car was running a bit rougher and if i'd stoped at a stop sign or red light, it felt like it was runnig on only three cylinders to the point of stalling. Now after a year or so, the problem is constent and a lot worse. A little note that might help, when i have time to open the hood before it stalls, i gently tap on the injeoctors and the problem is solved untill i step on the gas again then the problem returns. I cleaned the injectors, changed the cables, fuel filter, dist. cap...Please help me!
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I had a similar problem on a 2004 Jeep Grand Cherokee V8 engine.
Nothing seemed out of the ordinary except that occasionally the engine would run rough. Another seemingly unrelated symptom was that when shifting out of Park the transmission would sometimes jolt.
Turns out that I had a bearing on the serpentine belt tensioner that was freezing up. My belt broke and while I was changing the belt the pully on the tensioner fell into my hand. The bearing had seized and the plastic hub had disintegrated. After getting the new tensioner and belt. I noticed that the rough engine and the hard shifting transmission problems have gone away.
Seems that the engine was having to work harder to overcome the bad bearing.
Another cause of rough engines comes from dirty fuel injectors. The best solution I have run across is Chevron's Techron fuel additive. I had a honda Prelude that had a rough running engine. The Honda technician advised me to start adding Techron when I fill up. Worked like a charm. After the second tank I had no more problems. I have tried other fuel additives over the years, but Techron seems to be the best.
Also be sure to change your fuel filter. A dirty fuel filter will cause a noticeable drop in power.
No vacuum lock on fuel injection You have to diagnose the problem with a sequence of proper testing Check fuel pressure at the motor with a gauge Check for injector pulse & spark when it fails to start
I just recently have been fighting the same problem with the same make/model/year vehicle. For myself, I would drive off and on through the day and it would run fine. Then suddenly after a start it would run rough and die. I would have to wait 20 to 60 mins before it would start again. I had it checked and fuel pump was only putting out around 19 psi. It should be around 41 psi. Had fuel pump replaced and no more problems. Furthermore, now it runs so much better. It's funny how over time I didn't notice how the performance was slowly degrading. Unfortunaley fuel pumps for this car run around $300.
Try this: Remove the two (primary & secondary) vacuum diaphram covers & inspect the vacuum diaphrams. If there is any evidence of distortion at the diaphrams, expect to get the condition that you are describing.
I'm wondering if your injectors are leaking. If they are, and the car sits for a period of time like you're saying, fuel would puddle up and the car would run extremely rich until the excess puddled fuel burned off. Did you (or do you) notice black smoke from the tailpipe during the time the car is running really rough? Take a look and see - rev the engine if you need to, and see if you see some. It'd take a few minutes to burn off, and once it did, as long as the rest of the car is working right, you'd run normally. If you shut the car off for a short time (ie, getting gas, renting a movie) the car likely wouldn't sit long enough for enough fuel to puddle up for the condition to recur. If you park it overnight, that's plenty of time for the injectors to leak enough fuel for the car to run rough on startup.
No guarantee of course, but that's what sounds like a worthwhile investigation to me.