Delayed Throttle Response at high Speed
#1
Delayed Throttle Response at high Speed
Hi guys, I haven't been able to find a similar problem anywhere on the forums. The problem is this: I replaced all the exhaust gaskets on my 88 4WD Pickup and everything runs/sounds 10x better. I even feel maybe a little power increase. Although there are good effects after the overhaul, there are some suspicious ones as well. Now the truck seems to idle a little higher and when I hit 70-75 the throttle response is delayed by a 10-20 seconds. Is this a built-in governor? Or do I need to switch something in the MAF sensor? Any advice is appreciated.
Side note, the throttle delay didn't occur at 70-75 before I redid the exhaust. Truck is new to me since July.
Side note, the throttle delay didn't occur at 70-75 before I redid the exhaust. Truck is new to me since July.
#5
I haven't messed with the TPS yet. It's not stalling on me or bringing up a check engine light .... yet. But you're right, the other symptoms point to the TPS. Is there a way to adjust it? or does it require a full replacement/resetting?
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#9
A coworker thought maybe I bumped a vacuum hose, but all those are on the other side of the engine. The throttle response was "ok" at high speeds before I added the gaskets. Wouldn't you think if it was in the exhaust these symptoms would have occurred beforehand too?
I will likely replace the exhaust in the future anyway. I believe it to be all original
I will likely replace the exhaust in the future anyway. I believe it to be all original
#10
A coworker thought maybe I bumped a vacuum hose, but all those are on the other side of the engine. The throttle response was "ok" at high speeds before I added the gaskets. Wouldn't you think if it was in the exhaust these symptoms would have occurred beforehand too?
I will likely replace the exhaust in the future anyway. I believe it to be all original
I will likely replace the exhaust in the future anyway. I believe it to be all original
Should have nothing to do with speed either? Automatic transmission?
75 is kinda the useabl top speed, not sure if anything will respond. On my truck there is not really any response after 60. But there is a response - in tone motely, not in forward momentun. It takes it's darn time, will hit 100 in 39.5 miles or so
When you say response, what do you mean exactly? You step on it, and 30 seconds later it gets louder and starts to move?
Is your throttle cable correctly placed? At the rear of the engine, it should be wedged into a sort of "holder" tab.
Can you do a soundfile? Video?
#11
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A coworker thought maybe I bumped a vacuum hose, but all those are on the other side of the engine. The throttle response was "ok" at high speeds before I added the gaskets. Wouldn't you think if it was in the exhaust these symptoms would have occurred beforehand too?
I will likely replace the exhaust in the future anyway. I believe it to be all original
I will likely replace the exhaust in the future anyway. I believe it to be all original
If you haven't done so already you might want to reset the ECU trim memory.
#12
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iTrader: (-1)
Absolutely nothing AFAIK. Take off the cat and everything from the cat back (or leave it hanging) and go annoy some neighbors. Is the delay gone?
Should have nothing to do with speed either? Automatic transmission?
75 is kinda the useabl top speed, not sure if anything will respond. On my truck there is not really any response after 60. But there is a response - in tone motely, not in forward momentun. It takes it's darn time, will hit 100 in 39.5 miles or so
When you say response, what do you mean exactly? You step on it, and 30 seconds later it gets louder and starts to move?
Is your throttle cable correctly placed? At the rear of the engine, it should be wedged into a sort of "holder" tab.
Can you do a soundfile? Video?
Should have nothing to do with speed either? Automatic transmission?
75 is kinda the useabl top speed, not sure if anything will respond. On my truck there is not really any response after 60. But there is a response - in tone motely, not in forward momentun. It takes it's darn time, will hit 100 in 39.5 miles or so
When you say response, what do you mean exactly? You step on it, and 30 seconds later it gets louder and starts to move?
Is your throttle cable correctly placed? At the rear of the engine, it should be wedged into a sort of "holder" tab.
Can you do a soundfile? Video?
Definitely a video would go a long way here.. (The description is kind of vague)
#13
If it's not on that clip, it can get caugt by something and you have a racing away engine. You give it gas, and when you shift it redlines until valve float...
Ask me how I know. Lucky I had some space and thought of turning off the ignition fast.
#14
Now I've never driven a 30+ year old vehicle before. Could it just be normal? I'll try resetting the computer since that seems to be the cheapest route. Then I'll try with the exhaust. Figured I'd build up some opinions and flesh em out before I get too hot and heavy into engine repairs. I appreciate all the feedback and help I'm getting though. I'm somewhat new to the auto repair world. These little trucks seem to be a great first step for me.
#16
Does it have cruise control, and is it on?
It's not normal. But there are no sensors for what gear you are in, so - there is no correlation between the lag and the gear you have in it.
This some crazy weird behaviour
It's not normal. But there are no sensors for what gear you are in, so - there is no correlation between the lag and the gear you have in it.
This some crazy weird behaviour
#17
No cruise control, unfortunately. That'd be great for that drive. Been spitballing ideas with guys at work too. They all agree a good ol reset would probably help. Been busy so haven't had a chance to mess with it. Have some time tonight, then I'll test it over the weekend again.
Thankfully I'm not crazy. I didn't think it was normal behavior, but if it was I would have felt bad posting out here lol.
Thankfully I'm not crazy. I didn't think it was normal behavior, but if it was I would have felt bad posting out here lol.
#18
Registered User
iTrader: (-1)
Sorry everyone. First time posting here, so I'll try to clear up some details. The truck is a 5 speed standard. 1-4 work smooth and no delayed response. 5th is the issue and only at 70+ mph. I'll give a scenario. I drive 55 miles over the weekends to visit my parents. All highway speed. 30 miles of 65-70 mph in 5th gear works fine. No throttle delay, everything is working fine. I've even got up to 80 and it was fine (felt like that was about the max I wanted to try). Once I hit that 30-40th mile of the trip it becomes harder to maintain 70mph. I have to press more gas than the previous 30 miles and it will delay ~3-10 seconds and then jolt forward like I put my foot to the floor. So it feels like a yo-yo for the last 25 miles of the trip. Pressing gas, engine waits a few seconds then shoots forward, then let off gas to fall back to 70mph, rinse, repeat.
Now I've never driven a 30+ year old vehicle before. Could it just be normal? I'll try resetting the computer since that seems to be the cheapest route. Then I'll try with the exhaust. Figured I'd build up some opinions and flesh em out before I get too hot and heavy into engine repairs. I appreciate all the feedback and help I'm getting though. I'm somewhat new to the auto repair world. These little trucks seem to be a great first step for me.
Now I've never driven a 30+ year old vehicle before. Could it just be normal? I'll try resetting the computer since that seems to be the cheapest route. Then I'll try with the exhaust. Figured I'd build up some opinions and flesh em out before I get too hot and heavy into engine repairs. I appreciate all the feedback and help I'm getting though. I'm somewhat new to the auto repair world. These little trucks seem to be a great first step for me.
You will do the same/similar tests to the VAFM, a slight difference here is you might get a not so smooth curve with a glitch "in the avg rpm range" where the sensor is a bit worn out (they designed a fail safe so it's not a big deal like it would be if your tps went to half way and dropped back to zero).
Your likely hitting large hills the last portion of the trip? Overdrive is meant for cruising I wouldn't try to climb any big passes in it, nor expect to keep up with something with twice your horsepower. Lots of these are happy to hit 60mph, remember thirty years ago the speed limit was 55 almost everywhere.
You may also be hitting a load point where the clutch is starting to slip. Do the rpms shoot up right before you start to feel the acceleration?
#19
Your likely hitting large hills the last portion of the trip? Overdrive is meant for cruising I wouldn't try to climb any big passes in it, nor expect to keep up with something with twice your horsepower. Lots of these are happy to hit 60mph, remember thirty years ago the speed limit was 55 almost everywhere.
#20
Might start with the throttle and air flow meter tests, they're free. Measure the resistance on VTA on the tps while you sweep from closed to open throttle you should have a nice smooth curve no glitching, I don't recall off hand what it reads at full open since I prefer to do the voltage test instead. You also want to inspect the throttle plate movement is smooth and it reaches fully open.
You will do the same/similar tests to the VAFM, a slight difference here is you might get a not so smooth curve with a glitch "in the avg rpm range" where the sensor is a bit worn out (they designed a fail safe so it's not a big deal like it would be if your tps went to half way and dropped back to zero).
Your likely hitting large hills the last portion of the trip? Overdrive is meant for cruising I wouldn't try to climb any big passes in it, nor expect to keep up with something with twice your horsepower. Lots of these are happy to hit 60mph, remember thirty years ago the speed limit was 55 almost everywhere.
You may also be hitting a load point where the clutch is starting to slip. Do the rpms shoot up right before you start to feel the acceleration?
You will do the same/similar tests to the VAFM, a slight difference here is you might get a not so smooth curve with a glitch "in the avg rpm range" where the sensor is a bit worn out (they designed a fail safe so it's not a big deal like it would be if your tps went to half way and dropped back to zero).
Your likely hitting large hills the last portion of the trip? Overdrive is meant for cruising I wouldn't try to climb any big passes in it, nor expect to keep up with something with twice your horsepower. Lots of these are happy to hit 60mph, remember thirty years ago the speed limit was 55 almost everywhere.
You may also be hitting a load point where the clutch is starting to slip. Do the rpms shoot up right before you start to feel the acceleration?