Corolla Rough Idle After Timing Belt Change
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From: SlyckTom on 29 Aug 2006 19:31 Ok here it goes, I have a 1993 Toyota Corolla, 1.8 L, 4 cyl engine. It has 201,000 miles. The transmission is automatic. This weekend I decided to give the car its over due timing belt. Everything appeared to go well. While I was at it, I gave the car a tune up as well. When I first tried to start the car, it would not turn over. After pumping the gas and tinkering with the distributor, it finally started. However now the car idles very poorly. Here are the symptoms: 1) It idles very low... 2) ...which appears to make the engine (and car) vibrate. I have conducted some research into this, and the apparent reason is that the timing is off. However, I am very confident this is not the case. I justify this because: 1) The timing marks were aligned perfectly before reassembly. (even after rotating the engine several times.) 2) I was able to successfully set the timing to 10 degrees BTDC. 3) Once the care is moving, it runs very well and smooth - has lots of power. But here's the kicker... The reason I know its not the timing, is because the instructions call for two connectors on the diagnosis port to be shorted together before checking the timing. Once I do that, the car idles wonderfully for about 5 seconds, then goes back to poor idle. When I make the connection between the two connectors, there sounds like a vacuum is actuated within the intake manifold (specifically, the section before it branches out to the four cylinders.) It's not the new wires, cap and rotor either...I tried putting the old parts back on to no avail. I've checked the vacuum hoses, they all seem ok. This is an unbelievably frustrating situation. If anyone has insight into the problem, I would greatly appreciate it. Thank you, Tom
From: Ray O on 30 Aug 2006 00:31 "SlyckTom" <tom(a)slyck.com> wrote in message news:iii9f2h6e6hl04gifmfl7sc6k7196c9fl5(a)4ax.com... > Ok here it goes, > > I have a 1993 Toyota Corolla, 1.8 L, 4 cyl engine. It has 201,000 > miles. The transmission is automatic. > > This weekend I decided to give the car its over due timing belt. > Everything appeared to go well. While I was at it, I gave the car a > tune up as well. > > When I first tried to start the car, it would not turn over. After > pumping the gas and tinkering with the distributor, it finally > started. However now the car idles very poorly. Here are the > symptoms: > > 1) It idles very low... How low is low? What is idle RPM when the engine is cold and when it is warmed up? > > 2) ...which appears to make the engine (and car) vibrate. > > I have conducted some research into this, and the apparent reason is > that the timing is off. However, I am very confident this is not the > case. I justify this because: > > 1) The timing marks were aligned perfectly before reassembly. (even > after rotating the engine several times.) Are you talking about camshaft timing or ignition timing? Were the camshaft timing marke aligned perfectly AFTER reassembly? A poorly running engine is a symptom of one of the camshafts off by a tooth. If you are talking about ignition timing, you should always double check base ignition timing, especially after you fiddle with the distributor. > 2) I was able to successfully set the timing to 10 degrees BTDC. > 3) Once the care is moving, it runs very well and smooth - has lots of > power. > > But here's the kicker... > > The reason I know its not the timing, is because the instructions call > for two connectors on the diagnosis port to be shorted together before > checking the timing. Once I do that, the car idles wonderfully for > about 5 seconds, then goes back to poor idle. > > When I make the connection between the two connectors, there sounds > like a vacuum is actuated within the intake manifold (specifically, > the section before it branches out to the four cylinders.) Disconect the vacuum hose to the EGR valve and plug the disconnected vacuum hose with your finger and see if the condition clears up. If it does not, re-connect the EGR. > > It's not the new wires, cap and rotor either...I tried putting the old > parts back on to no avail. > > I've checked the vacuum hoses, they all seem ok. See if you can measure manifold vacuum. You should have above 16 in Hg at idle. > > This is an unbelievably frustrating situation. If anyone has insight > into the problem, I would greatly appreciate it. > > Thank you, > > > Tom > Check the idle air control valve, look for cracks in the intake tube between the air filter housing and the throttle body. -- Ray O (correct punctuation to reply)
From: toyomoho on 30 Aug 2006 00:23 It is normal when the two connectors are linked for the idle to pick up for a few seconds then drop back to “normal.” On one occasion it took several timing attempts to get the car to idle right (instead of barely idle). Did you knock a vacuum hose loose, a wire to sensor? Might look again at the distributor, as this seemed to be a problem after the belt was changed. -- toyomoho ------------------------------------------------------------------------ toyomoho's Profile: http://www.toyotanation.com/forum/member.php?userid=59151 View this thread: http://www.toyotanation.com/forum/showthread.php?t=153351
From: SlyckTom on 30 Aug 2006 18:42 >How low is low? What is idle RPM when the engine is cold and when it is >warmed up? This is hard to tell, since I dont have an RPM gauge. But I can tell you that it idles slightly better when warm than cold. >Are you talking about camshaft timing or ignition timing? Were the camshaft >timing marke aligned perfectly AFTER reassembly? A poorly running engine >is a symptom of one of the camshafts off by a tooth. I am talking about both the camshaft and ignition timing. And yes, they were both aligned after reassembly. I would understand if it was off by a tooth if the engine performace was terrible, but it is not once I am out of idle. In fact once Im driving it runs better than ever. >Disconect the vacuum hose to the EGR valve and plug the disconnected vacuum >hose with your finger and see if the condition clears up. If it does not, >re-connect the EGR. No EGR valve on this model... >See if you can measure manifold vacuum. You should have above 16 in Hg at >idle. Manifold vacuum is on the money. But here is some progress that I have made: I reset the computer, and the car idles somewhat better - not perfect but not nearly as poor as before. Also, and this may be the first real sign of progress, if I disconnect the Throttle Position Sensor, the car idles perfectly. Another point I should make...I gave the engine a good power washing after the job, and in the process appear to have made an exhaust manifold gasket leak worse (cleaned eons of oil reside out). I wonder if the introduction of air towards the O2 sensor perhaps is throwing something off? Thank you again, TOm On Tue, 29 Aug 2006 23:31:53 -0500, "Ray O" <rokigawaATtristarassociatesDOTcom> wrote: > >"SlyckTom" <tom(a)slyck.com> wrote in message >news:iii9f2h6e6hl04gifmfl7sc6k7196c9fl5(a)4ax.com... >> Ok here it goes, >> >> I have a 1993 Toyota Corolla, 1.8 L, 4 cyl engine. It has 201,000 >> miles. The transmission is automatic. >> >> This weekend I decided to give the car its over due timing belt. >> Everything appeared to go well. While I was at it, I gave the car a >> tune up as well. >> >> When I first tried to start the car, it would not turn over. After >> pumping the gas and tinkering with the distributor, it finally >> started. However now the car idles very poorly. Here are the >> symptoms: >> >> 1) It idles very low... > >How low is low? What is idle RPM when the engine is cold and when it is >warmed up? > >> >> 2) ...which appears to make the engine (and car) vibrate. >> >> I have conducted some research into this, and the apparent reason is >> that the timing is off. However, I am very confident this is not the >> case. I justify this because: >> >> 1) The timing marks were aligned perfectly before reassembly. (even >> after rotating the engine several times.) > >Are you talking about camshaft timing or ignition timing? Were the camshaft >timing marke aligned perfectly AFTER reassembly? A poorly running engine >is a symptom of one of the camshafts off by a tooth. > >If you are talking about ignition timing, you should always double check >base ignition timing, especially after you fiddle with the distributor. > >> 2) I was able to successfully set the timing to 10 degrees BTDC. >> 3) Once the care is moving, it runs very well and smooth - has lots of >> power. >> >> But here's the kicker... >> >> The reason I know its not the timing, is because the instructions call >> for two connectors on the diagnosis port to be shorted together before >> checking the timing. Once I do that, the car idles wonderfully for >> about 5 seconds, then goes back to poor idle. >> >> When I make the connection between the two connectors, there sounds >> like a vacuum is actuated within the intake manifold (specifically, >> the section before it branches out to the four cylinders.) > >Disconect the vacuum hose to the EGR valve and plug the disconnected vacuum >hose with your finger and see if the condition clears up. If it does not, >re-connect the EGR. > >> >> It's not the new wires, cap and rotor either...I tried putting the old >> parts back on to no avail. >> >> I've checked the vacuum hoses, they all seem ok. > >See if you can measure manifold vacuum. You should have above 16 in Hg at >idle. > >> >> This is an unbelievably frustrating situation. If anyone has insight >> into the problem, I would greatly appreciate it. >> >> Thank you, >> >> >> Tom >> > >Check the idle air control valve, look for cracks in the intake tube between >the air filter housing and the throttle body.
From: Ray O on 30 Aug 2006 21:28 "SlyckTom" <tom(a)slyck.com> wrote in message news:jl4cf2td91rn8kij1aj8nor3mee8co9jet(a)4ax.com... > >How low is low? What is idle RPM when the engine is cold and when it is >>warmed up? > > This is hard to tell, since I dont have an RPM gauge. But I can tell > you that it idles slightly better when warm than cold. > >>Are you talking about camshaft timing or ignition timing? Were the >>camshaft >>timing marke aligned perfectly AFTER reassembly? A poorly running engine >>is a symptom of one of the camshafts off by a tooth. > > I am talking about both the camshaft and ignition timing. And yes, > they were both aligned after reassembly. I would understand if it was > off by a tooth if the engine performace was terrible, but it is not > once I am out of idle. In fact once Im driving it runs better than > ever. > Yup, that seems to rule out a mis-timed camshaft. >>Disconect the vacuum hose to the EGR valve and plug the disconnected >>vacuum >>hose with your finger and see if the condition clears up. If it does not, >>re-connect the EGR. > > No EGR valve on this model... > >>See if you can measure manifold vacuum. You should have above 16 in Hg at >>idle. > > Manifold vacuum is on the money. > > But here is some progress that I have made: > > I reset the computer, and the car idles somewhat better - not perfect > but not nearly as poor as before. > > Also, and this may be the first real sign of progress, if I disconnect > the Throttle Position Sensor, the car idles perfectly. > > Another point I should make...I gave the engine a good power washing > after the job, and in the process appear to have made an exhaust > manifold gasket leak worse (cleaned eons of oil reside out). I wonder > if the introduction of air towards the O2 sensor perhaps is throwing > something off? > > Thank you again, > > TOm > I doubt if the O2 sensor is causing the rough idle. Does the car have an idle air control valve and if it does, have you checked it out? -- Ray O (correct punctuation to reply)
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