Hesitation / delay from stop

D

drallan

New member
Hi,
New 99 Ltd w/ 138k owner here. I've done some searching on the forum but haven't found anything exactly describing my symptoms.

When stepping on the gas from a stop I have a slight delay / hesitation before the engine revs up and she takes off. Once moving, acceleration is smooth and quick. This also occurs when manually opening the throttle via throttle body in engine bay (did some sea-foaming and TB cleaning). And I think it also happens when taking my foot off the gas for a few seconds while cruising down the road, then stepping on it.

It almost feels like the engine is going to die then it catches itself, I think I've heard it backfire when I really step on it from a stop. There is no delay when passing or accelerating from a slow roll. Only when my foot is completely off the gas, then I step on it. Other than this she runs great and smooth. Idles around 700-800 w/o AC on and 1200 or so w/ AC on. It does have a new (autozone brand) TPS. I haven't had a chance to pull and inspect the plugs yet. I plan on ordering new plugs, wires and fuel filter this week and tackling them next weekend. I've driven about 100 miles on it. No Check engine light, but I haven't scanned the codes yet.

Any suggestions or thoughts? Reset CPU? Fuel Pump? Fuel Pressure Regulator? Another round of Sea-foam or Injector cleaner?
I don't want to just start throwing parts at it.

Thanks,
Dustin
 
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My 01' had the exact same symptoms and it got better (less) after I put new plugs, wires, pcv and fuel filter in. After that, it was only there (hesitation) when it was cold.

Others have posted about the same problem, so if you search, you'll probably finds lots of material on it. I just went with the tune-up and it helped.
 
I'm gonna hit up the Toyo dealer this afternoon and pick up a new pcv, fuel filter and plugs. I'm not sure the age or condition of old plugs, but if I'm going to pull them to inspect I might as well replace. Especially since they are relatively cheap. I like to know the age/condition of regular maintainance items of new vehicles.

I did not replace the TPS, the previous owner did. I guess I shouldn't have said new as I'm not sure exactly how old it is (but it is significantly cleaner than anything else in th engine bay). I found the old one in an autozone box in the glove compartment.

I'm not sure if he was trying to trace down the same issue or if he had a bad TPS. I guess I could put the old one on and see if I get any codes or if it drives worse.
 
So I changed out the Spark Plugs (not wires, but they look good), Fuel Filter (both from dealership), pcv, seafoam, TB clean, MAF clean, and a couple tanks of Techron, disconnected battery for 20min, and I still have had no luck. She runs great 99% of the time, just hesitates from a stop. Almost feels like it is going to die sometimes. Especially the harder you step on it. If I'm cruising around w/ just the smallest bit of throttle she accellerates great. I'm getting around 16-17 mpg on 265/75/16's (stock otherwise).

Unless anyone has other suggestions, it looks like I'm gonna be replacing the pump. I might end up replacing the fuel sending unit at the same time (might as well while I'm in there), as my wife has noticed the gauge occasionally reading full when she knows it is only about 1/2. Which apparently is a known issue w/ this gen of T4R.

A couple questions:

1. Any other suggestions to try before I tackle the fuel pump?
2. In the past I've had other fuel pumps either work or not work, but never this sorta work. Can I get by for a while before fixing it, or is this the sign that it is on it's last leg?
3. Are there any good write w/ pics on replacing the fuel pump? I've searched and found a few, but nothing w/ specifics. More along the lines of "Disconnect hose/wiring, drop tank, replace, put back together".
4. Do I have to drop the tank or is there an easier way? I've read about the cargo area access pannel, but don't know if I can change the pump through it.
5. Do I have to change out the gauge cluster board if I change out the fuel sending unit in order to fix the gauge issue (which is 2ndary right now)?

Thanks for any help!
 
You said it does the same thing when manually opening the throttle on the throttle body, you sure your throttle isn't sticking or something. I don't think it would quite case what you're having but it would give the acceleration a delay. Check and make sure all the hoses are in the right spots and none are popped off. They're easy to miss.
 
Yeah, it does it either from pushing the pedal or manually opening the throttle. I did just tighten up both the throttle and shift cable a bit. I is more responsive and the hesitation is now shorter, but it is still there. I've checked all the vacuum hoses I can see and they are all hooked up. It is a new to me vehicle so I haven't had a chance to double check and verify that they all are going to the right places, but they all seem to fit as they should. Some are a little cracked around the ends so I tightened them up w/ some electrical tape to make sure they stay on snug.

Does anyone have a good vacuum diagram so I can trace through them all?

It's to the point where I don't always feel comfortable trying to merge into fast moving traffic. I have to either make sure I am slowly rolling forward, or anticipate a delay and step on the gas a second earlier than I would normally. The only way I really know how to describe it is that it is like the engine dies for a sec then catches itself. Sometimes I think I can see the headlights/dash lights dim slightly when it hesitates.
 
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99 4runner limited

i also have the same issue with my 4runner. have changed plugs, replaced fuel filter, ran sea foam through and still have the hesitation when pressing the gas from take off. throttle body looks clean. feeling unsafe merging quickly between traffic. did you change your fuel pump and did that work??
 
Any codes?

Don't overlook ignition wires. It's a cheap and easy swap and the originals wear more over time and heat than due to mileage.

Also, have you cleaned your MAF sensor?
 
This sounds very similar to some problems I've been having with my trac/vsc. Do you ever get those VSC lights flashing during this problem? Of course it would make no sense to me that this would happen in park.
 
drallan said:
Hi,
New 99 Ltd w/ 138k owner here. I've done some searching on the forum but haven't found anything exactly describing my symptoms.

When stepping on the gas from a stop I have a slight delay / hesitation before the engine revs up and she takes off. Once moving, acceleration is smooth and quick. This also occurs when manually opening the throttle via throttle body in engine bay (did some sea-foaming and TB cleaning). And I think it also happens when taking my foot off the gas for a few seconds while cruising down the road, then stepping on it.

It almost feels like the engine is going to die then it catches itself, I think I've heard it backfire when I really step on it from a stop. There is no delay when passing or accelerating from a slow roll. Only when my foot is completely off the gas, then I step on it. Other than this she runs great and smooth. Idles around 700-800 w/o AC on and 1200 or so w/ AC on. It does have a new (autozone brand) TPS. I haven't had a chance to pull and inspect the plugs yet. I plan on ordering new plugs, wires and fuel filter this week and tackling them next weekend. I've driven about 100 miles on it. No Check engine light, but I haven't scanned the codes yet.

Any suggestions or thoughts? Reset CPU? Fuel Pump? Fuel Pressure Regulator? Another round of Sea-foam or Injector cleaner?
I don't want to just start throwing parts at it.

Thanks,
Dustin
Click to expand...

I would start by busting out the multi-meter and checking the ohms of the oem toyota tps that the old owner replaced. FSM says that the ohms between terminals E2 and VC (which are the 2 outer most terminals {there are 4 terminals on the sensor}) should be between 1200 and 3200 ohms. If the sensor checks out, I would put the oem one back on. That way you aren't constantly wondering about some aftermarket part that may be faulty.

Is the computer storing any codes? hook up a scanner to rule out the possibility of the old owner taking the check engine bulb out of the dash. Most faults with the TPS, throttle body and ECM would set a code for you to pull.

While the scanner is hooked up, you should also be able to have it tell you the TPS position %. You can press the pedal through it's range of motion to see if it is operating as it should.

I think you're probably going to need a FSM to get into this one. Diagnostics for something like this can get a bit intense. I wouldn't start throwing parts at it as that is very likely going to just be a waste of money.
 
Not sure about the 5VZ-FE but, but on my 3RZ the TPS sensor is very touchy, you need to get the adjustment just right. I had similar symptoms after replacing my TPS and needed to re-adjust a few times before getting it right.
 
So I didn't realize this thread had been resurrected. Luckily I was able to solve the problem back when it happened. It ended up being a dirty/poorly cleaned MAF if I recall. I took it off again and there was a little blob of something on the wire. I hit it with the spray again, also get down inside all the tubes and holes, and it ran good as new.

Some other options, I recently had an intermittent Cyl 6 misfire that would bog down under load. It turned out to be a bad plug boot. I'm fortunate that I now have an 04 Tundra w/ the 5Z engine and could do some quick and easy part swapping to help troubleshoot.
 
I have this issue as well, no CELs, I've hooked techstream up to it and ti shows everything checks out fine, I will say, if you do the ANDY mod itll fix it but it also turns the VSC lights on the dash is the only tradeoff, I dont like lights so I'm trying everything to fix this, I will be replacing my wheel speed sensors and then the only next step is the ABS ecu, I have put in a new fuel filter and even tank and pump and there is no difference whatsoever
replaced: MAF
Fuel filter
Fuel pump
Fuel tank
Wires and plugs
Throttle Position sensor
 
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Mangis17 said:
I have this issue as well, no CELs, I've hooked techstream up to it and ti shows everything checks out fine, I will say, if you do the ANDY mod itll fix it but it also turns the VSC lights on the dash is the only tradeoff, I dont like lights so I'm trying everything to fix this, I will be replacing my wheel speed sensors and then the only next step is the ABS ecu, I have put in a new fuel filter and even tank and pump and there is no difference whatsoever
replaced: MAF
Fuel filter
Fuel pump
Fuel tank
Wires and plugs
Throttle Position sensor
Click to expand...
Have you tried pulling ABS codes instead of throwing parts at it?
 
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