Hi,

Please help me.

While I'm driving at a constant cruising speed on freeways, my car suddenly drops power and downshifts to the next lower gear, and regains power and shifts back up. The whole violent event happens within 1.5 second. And it happens randomly, sporadically, absolutely no patterns.

I recently replace the fuel filter and had the injector cleaned too. I thought that that would fix the problem. But, nope.

I hope it's not the transmission. Is it?

Please give me your take on this. I am clueless. I can't take it to the mechanics, because I can't really show them the problem. It happens so random.

Thank you.

Oh, if I drive with "Over Drive" on, the problem doesn't occur. But, it drinks gas like crazy.

 

Alternator?

 

It could be a fuel injector issue too. And don't drive on the highway with your OD off, dude. It WILL gulp gas....it is only meant to get higher revs via downshifting when either you want a sudden burst of speed, towing something or climbing a hill, etc.

 

Hi,

I just had the fuel injector cleaned professionally. But the problem persists. Originally, I thought the fuel is getting clogged or something of the sort. But, I replaced the fuel filter and professionally cleaned the fuel injector. There's sonething else that's going on.

 

What year and model is your max? VE or VG engine?

 

Hi,

Sorry, it's a 1994 GXE with 125K.

 

Sorry, not know much about the VG engine, I've got a VE. But have you checked your plugs and rotor. I've heard of these causing hesitation and power loss.

 

Hi,

Not so long ago, I installed a set of those NGK Platinum spark plugs. The mechanic said that those should last for at least 25K before replacement. I'll look into the plugs though, but I doubt that they're the culprit.

The random nature of the hesitation and power loss is what puzzling. But, only during constant speed. Not during acceleration nor deceleration.

 

have you checked your distributor cap? ignition coil? any oxidation there can cause sudden loss of power.

 

also, do u mean that it loses power first and then slips into lower gear or vice versa? if former is the case, then rest assured, it isn't your transmission.

 

I think you meant if you drive with the OD off....right? when the yellow OD light comes on, it means you have turned OD it off, not on.

 

Hmm, no, I haven't check any of those. I will certainly do that tomorrow. I'll take in to the mechanic and have him check the distributor gap and ignition coil.

Thanks.

But, do you think that the transmission gear, especially, the 4th one, gone bad, and causing the slipping/sudden hesitation?

 

i am on a roll here!

 

It happens so fast. I don't quite know which came first. But, I think it loses power first, then slips into the lower gear. Then, bamm, it surges back to the original gear.

 

Yeah, I drive with the light on. And get like 5 mpg. I only do it when my wife is in the car. She's afraid of the sudden hesitation and jerk.

 

I'd put my money on the transmission having a problem in the overdrive "circuit"

 

Sorry dude, I meant distributor "cap". There is no such thing as distributor gap....LOL. I was d*mn sleepy when I posted that.

I also agree with ITM's suggestion on the OD circuit.

BTW dude, what do you mean you drive with the OD off (yellow light on) as your wife doesn't like the jerk of sudden acceleration? Having OD on (light off) actually makes your drive smoother (not to mention quieter and more economical as your RPMs go down) on the highway.

 

SImple scientific method here--problem with the overdrive engaged, no problem with overdrive not engaged = problem with overdrive. Also agree with ITM (shouldn't it be IAM?)'s suggestion of the OD circuit itself. Used to have an old VOlvo that had an overdrive that would cut in and out the same way. Had to do a little rewiring. In your case, might be a little more expensive, but what do I know? I don't have an automatic. Good luck!

 

Sorry, I think I just confused everybody.

The sudden&random hesitation and power loss occur when I'm driving at a constant speed on the freeway with O/D on (yellow light off).

However, I notice that if I push the button and turn the O/D off (yellow light on), and drive like that, the problem goes away.

Yeah, with the yellow light on, I get terrible mpg and putting lots of stress on the engine. I only do it when my wife is with me, thank God not that often

 

yup, the trans needs work

 

What's the estimated cost of a trans rebuild?

 

Depends on who does it and the quality of the work.
good ones appear to be in 1500+ range

 

Trans rebuild may be a long shot though. Find a trustworthy mechanic and have him check the trans wiring for OD. Be careful though, 9/10 times they will ask you to get it rebuilt just to milk you for cash.

 

I have the same problem with a 92 SE manual.
Car surges on highway when I am at constant speed.
I noticed several people in the forum having this pb, (surge, hesitation,
stalling). There is a pattern here and all these cars might have same pb.
I have not found someone who has located the pb yet. I think nothing is
wrong with your transmission or OD, but I agree with possible ignition problem
or eng. temp. sens. pb.
In any case please let me know once it is fixed. Thanks.

 

I am going to check the coil packs for cracks and sparkplugs (->NGK OEM is best) to see if that's the pb on my car ( thks RedMax92SE).

 

i dont know much about the smaller motor either

 

Ericw, your problem is probably different from the one being discussed. If it were an ignition problem, you should likely have some drivability problems that are consistent. How would you explain an ignition problem that reliably goes away every time the OD is switched off?

 

I'm almost 100% sure it's the tranny. I had the same exact problem. it would drive fine w/ the overdrive off, but when i'd turn the overdrive on the gears would slip and wasn't very driveable over 3rd gear. I've had my tranny rebuilt twice within the past 2 years.

 

Over a year ago I had all the same symptoms you are describing. I don't think it's your tranny otherwise it think you would see it happen more often.

When crusing down the highway or under slight acceleration out of nowhere I would loose powder for a few seconds. If I kept my foor on the gas I would not regain any powder until I completely removed my foot off the gas. If I removed my foot of the gas as soon as it happened I would regain powder much faster.

Boy, did I think twice about pulling into on coming traffic or while attemping to pass someone.

After trying several things it ended up being my Knock Sensor.The following is a list of everything I did.

92 SE

• Replaced plugs,
• Cleaned TB
• Fuel Injection Service
• Replace Fuel Filter
• Cleaned and applied dielectric grease on all connectors I could reach (TB, Air Mass, etc..)
• Checked O2 Sensor

It ended up being my Knock sensor, I had this problem for months and couldn't figure it out. I never got a "Check engine" light nor did the ECU have any trouble codes. I guess if the sensor works intermittently like mine did it didn't set of any codes.

Someone on this site suggested that I try the Knock sensor....low and behold once I put everything back together with the new sensor the problem went away and it seemed to have more powder than before.

My engine is the VE which has the Knock Sensor the "V" section of the engine block under the intake manifold. I was quite a job to replace if you have the VG engine from what I hear it should be a bit easier.

BTW the sensor was corroded fairly bad.

Hope this helps...

 

This is very helpfull, thanks igramwest.
100% match with my car symptoms, + I own the same model.

How big a job is it to replace the knock sensor ? (I admit I don't know zilch about it). Can I easily check the part for the corrodation that you describe. How much did it cost you ?

prenobi, do you also notice the same behaviour when the pb occur with the
gas pedal as igramwest described, if you do then I still think you have the same pb.

Eric

 

I'd say if you are an average do it your selfer you can do this in 4 to 6 hours. If you feel uncomfortable with getting into your engine I would suggest not even attempting it and paying someone. If you do attemp this, a word of caution, buy the intake plenum and manifold gaskets before you do this job. Also have some high temperature RTV as you will need it when you remove the intake manifolds there's a water tube that runs from the front to the back of the engine. You'll need to remove that tube to get access to the knock sensor, if you have the right size crows foot wrench you might not need to remove this tube. If you can get the gasket for the tube before hand then you shouldn't need the RTV. I'm not sure what this tube gasket is called.


I took some pictures when I replaced mine, I'll see if I can find them and post them.

Not sure how to post pictures....if anyone can send instructions I would appreciate it.

 

ok my 90 HJ30 has the same symptoms, changed the spark plugs and PCV plug and everything worked for a couple of days. so I think its the Knock sensor,

now spending 90$ on some piece of plastic just doesnt do it for me... is there some kind of resister that can be used inplace of this thing?

edit : igramwest if you email me the pics at jjuroch@miami.edu I can host the pics ...

 

Only if you plan on replacing your motor

 

qI agree with intenetautomar. You might end up replacing your engine if you try something like that.

The part may look like cheap plastic but it's one critical sensor that helps with engine performance. You can see from the pictures that cq107 will post that may sensor had corroded terminals and the plastic housing was cracked.

The purpose of the knock sensor is to tell the onboard puter when to stop advancing the timing. The timing on our cars is puter controlled, when the knock sensor senses that the car is beginning to knock or ping it no loner advances the timing. My understanding is that these sensors are much more sensitive than our hearing; they can detect/hear the knock before we can.

I found some sights that explain it in better detail than I can.

http://www.autoshop101.com/forms/h38.pdf

http://www.misterfixit.com/deton.htm

I've sent the pics to cq107....

 

No mod's

Intake Plenum removed

ks under tube 1

ks under tube 2

new vs old

 

hmm, I have the SOHC engine, but experince all of the laggy ness and other powerloss mentioned above after new sparkplugs... could it be the knock sensor is messed up ? there is only 90k miles on the car...

 

Anything is possible,
Have you checked your timing ?

 

I've been running the resistor mod w/ my JWT ecu since the summer. If it's cold out, it's fine. Once it gets hot, it's better to have a functioning KS.

The ks doesn't actually keep the engine's timing from advancing more. The ecu has a pre-mapped ignition advance/retard curves. If the KS detects knock while the ecu is on one of these curves, it will pull back the timing quite a bit until the knock is gone. If you use good enough gas and the weather is cold enough, the engine won't knock on the ign maps and the resister prevents a corroded/malfunctioning ks sensor from reaching the ecu.
Use at your own risk. At the very least, it's a good tool to use to diagnosis a bad ks. Especially for how expensive one costs and how labor involved the replacement is.

 

well new timing belts at 60k and 83k miles (due to a new waterpump replacement). Distributer is not cracked at all...
The loss in power only happens when the car is at tempature and radiator fans are on...
i don't know what else to check for with timing...

 

I believe you should look at the water temp sensor connetor. If it's corroded like the KS pic above, it will increase the resistance and send a false temp signal to the ecu and make the ecu think the engine is hotter than it really is. On the VG I believe it's read like the VE. Position? I forget.