Engine surging.


Asked by Apr 21, 2012 at 11:26 AM about the 1989 Toyota Camry

Question type: Maintenance & Repair

When I bought this car, 89 Toy Camry, it'd
been sitting awhile. After start-up, and after
it reached operating temperature, the engine
started surging. At an standstill, it's never
done it again, but while driving, at any
speed, but usually between 20-50 mph, the
engine will surge up and down 3-500 rpms.
Only while coasting or deceleration. Cap,
rotor, wires, plugs, water pump, and timing
set have been replaced. The car runs like a
top, but the surging is getting worse. Help?

11 Answers


Sounds like a fuel issue...Try running some fuel system cleaner thru the fuel tank...After setting a while fuel turns into varnish...Nasty stuff...

5 of 5 people found this helpful.

I forgot to mention, I ran fuel system cleaner through, and changed both the fuel & air filters. I drive it about 240 miles a week with no other problems except this annoying surge, which unfortunately seems to be getting worse, happening more frequently.

1 of 1 people found this helpful.

Could be a weak fuel pump or fuel pressure regulator if so equipped...

1 of 1 people found this helpful.

Thanx for your suggestion, but after careful thought and consulting a mechanic, we concluded this probably isn't fuel related. Car accelerates cleanly, and holds steady on heavy load &/or incline. The only time the problem occurs is while coasting. I just replaced the O2 sensor with little improvement. EGR & PCV valves have been ruled out. Is there an idle sensor, or such a thing as a deceleration sensor or solenoid? A shop wants to charge over $100, and won't guarantee they'll even find the problem!

1 of 1 people found this helpful.

Have you checked for vacuum leaks? They are a common cause for surging...

2 of 2 people found this helpful.

I just took a look a few minutes ago. Vacuum lines appear almost new. Checked connections, but there's dozens of 'em! I need to check again tomorrow when it's light & not so cold, with the engine running, and a can of carb clean in hand. I did discover the car has CA emissions, and a "downstream" O2 sensor I missed earlier. Why do CA cars have 2 sensors, and if the "upstream" sensor is new, could the surge, (only while coasting between 900-1500 rpms) be caused by the 2nd sensor? EGR valve is basically for recirculating exhaust gas on start up only , isn't it? Can it cause fluctuations after warm up too? What does the MAF sensor control? And why would a coolant temp. sensor cause surging?! Sorry, I've been researching and have come up with lots of questions, but no real answers...

5 of 5 people found this helpful.

O2 sensor may be it...EGR works continously to cut down on NOx by lowering combustion temp...Sometimes they need cleaned or replaced...MAF is the mass air flow sensor...Located just before the air cleaner on the intake tube...It measures incoming air volume so the computer can adjust air/fuel mixture...How about the throttle position sensor? I had an F150 that had a bad one the had a sticky spot and would surge on either side of the sticky spot...Just happened to be at 55mph...

1 of 1 people found this helpful.

I thot about the TPS, and may be over thinking things, but the surging happens at pretty much any speed between 20-50 mph @ low to mid range rpms, and only while coasting. Touch the throttle or even the brake, and the surging stops. Lately, I've begun to notice a VERY faint miss @ hiway speeds while maintaining speed, but it's never consistant, nor strong enough to overly concern me... (except, I did replace all those obvious parts already...hmmm...)

1 of 1 people found this helpful.

By the way... Thank you for taking the time to help out! I appreciate it!


I know this sounds crazy, but it sounds like no heated coolant is passing thru your iacv (idle air control valve), could be air an bubble in your cooling system, plugged iacv coolant hose, (by the thermostat housing is a small coolant hose that twists and turns, and goes under the throttle body), if this small hose gets plugged, rust, debris, or old radiator stopleak, or even an air bubble from filling a cold radiator wrong), your iacv thinks the engine is cold, but the rest of your engine knows its warm, the engine temp sensor, cold start injector, water temp sensor, all tell the computer one thing, the iacv tells it another, and tries to speed up the idle because the cold engine requires more fuel, point being the computer is trying to compensate for something. this is why the brakes, idle, coolant, fuel all seem sorta connected to, but not the reason for, your problem. 1 check radiator for reduced flow(plugged, or restricted), 2 see if an air bubble is in the cooling system, behind the thermostat(remove cap, run motor till thermostat opens, top off coolant) 3 check to see if iacv hose is blocked, it twists and turns and is way smaller then other coolant lines, it can be clogged, 4 if all this helps your iacv works, but was not working because the heat it needed to close was insufficient, in my case replacing my radiator was the fix, when I started looking at this problem you could not have convinced me the radiators restricted flow was my problem and my solution was so simple. good luck oh yeah the only thing that concerns me was on my truck the surging was when I applied the brakes, for you it stopped with brake application so im concerned our issues may differ, good luck and please let us know what works for you so we can get better performance for us too.

2 of 2 people found this helpful.

I am not sure how old this post is but i too have a 1989 Toyota Camry i have the exact same surging issue. But i come with your solution... i have changed cap, rotor, spark plugs, wires, coil pack, pcv valve, and i have checked pressure of all cylinders as well as fuel pressure all in one and individually at each injector. I have replaced the fuel filter and checked and or replaced every sensor on this car.... Now why i am telling you is for this simple reason of what i have not cleaned or changed... 1 Is the EGR Valve mine well lets just say 29 years and not one cleaning...so with that and the combined issue with a sticky throttle i have narrowed down the search. My problem as well as i hope solves your problem too is that darn purge canister replace that and your problem should disappear. If it does not then back trace your steps or problem solve....what i mean is start your car let it warm up to temperature and one by one unplug a sensor if you notice the engine die, or a drop or spike in rpms thats not your issue. If you get to say the tps like i did and unplug it and notice nothing change, replace the sensor but like i said my problem was a sticky throttle a plugged egr and a purge canister that went 29 years purging on. Hope this helped. good luck

1 of 1 people found this helpful.

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