Engine/Transmission (1998.5 - 2002) Hesitation Problem

[trqmnstr]

Hey Everybody, I recently started having a hesitation when accelerating and at a constant speed. It started about a week ago and I sure hope it's not the VP. It feels like I'm backing off the throttle when I'm actually not. Today, I tried to accelerate in 6th gear at about 1600rpm and it took a split second for it to kick in. It usually takes right off. I reset the APPS and it cleared up for two days and now it's getting worse. I also just cleaned the IAT which was already clean. I have a FP gauge on the way so I can check that in a few days. Someone mentioned that the K&N filter gets the MAP dirty and it has to be replaced. Any suggestions? Thanks in advance.

 

[Gary - K7GLD]

For absolute starters, we need fuel PSI to the VP-44 - otherwise it's just a big guessing game with LOTS of possibilities!

 

[trqmnstr]

I hear ya on that one Gary. I'll report the FP ASAP. I was thinking of cleaning the grounds like I've read in a lot of posts. What's the proper procedure for that - just rough the surfaces and brake cleaner maybe?

 

[KDoerr]

Make sure that the pumps are all working and good luck

 

[Gary - K7GLD]

As a quick check, you might change the fuel filter - that alone will largely cover 2 areas of possibility - if the old filter is clogged, it can do what you describe, and if the lift pump will refill the fuel filter canister with reasonable speed and ease, chances are it's in decent shape... You could still have remaining fuel delivery problems, but that at least hits a couple of the biggest possibilities...

 

[trqmnstr]

I just changed the fuel filter and bumped the starter once and let the LP run for 20-30 seconds - she fired right over. I also have no codes and even had AutoZone scan with no codes. I bought this truck with 145k on it so I don't know the history. Could the APPS be causing this. I find it strange that an APPS reset made it go away and then came back in a few days.

 

[Gary - K7GLD]

Yes, APPS would be a prime suspect - even moreso if the reset temporarily seemed to correct it...

 

[trqmnstr]

I just disconnected the batteries to perform another APPS reset. We'll see what happens. I assume that if this temporarily fixes it again and then returns, the problem is most likely the APPS. Am I correct? I'd rather spend $300 than $1200 for a VP. Let's hope for the best. Gary - I sent you a PM.

 

[trqmnstr]

I did the APPS reset and the truck ran so nice. It ran as smooth as it used to. I only felt the hesitation a couple of times. Is it possible that the reason it runs better is because of the batteries being disconnected overnight and not from the APPS being reset? Any suggestions would be great. I'm sure that it will come back soon as it did with the last APPS reset.



Geno's just told me that my FP gauge is on backorder, so now I have to wait an extra 10 or so days. I hate it when that happens.



Gary, thanks for the BHAF info. I'm going to buy one in the next few days.

 

[ABarrey]

I had the same thing-twice-both were sucker pumps going out. Felt like a dead peddle when I tried to accelerate from steady downhill at 65. Dealer couldn't find any codes-second time it took out the VP before it was done. It was on warranty but lotta lost time. Now I have a FASS - all good so far. I'd get the FP checked before you go too far.

Good luck

 

[trqmnstr]

ABarrey, thanks for the response. I think I'll go ahead and buy a new lift pump. My FP gauge is on backorder and 10 more days with a bad lift pump could lead to you know what. Thanks again.

 

[trqmnstr]

I installed a new lift pump today and she still has the hesitation. It does seem to have a little more power though. I think I got a few psi out of the new pump. So now I'm back to the APPS. Any thoughts? Thanks



Also, whenever I finished the LP install I bumped the starter a few times and she fired off like always. I thought they were supposed to run rough and smoke trying to get the air out of the lines.

 

[ABarrey]

Oh man, I hope it's not your VP!! Good luck, and let us know what you find.

Andy

 

[DLBurns]

Try checking ALL of your connections for moisture, blow them out with compressed air like the stuff that comes in a can for computers and then coat them with dielectric grease. While you are in there check the pins to insure they are all straight and making good connections.

I had the same problem as you and found that it was a bent pin in connection C-125 on the firewall above the valve cover!

I had replaced my APPS, both batteries, high and low pressure AC switches and cleaned EVERY ground and connection I could get to all to no avail and at a cost of $650. 00 smackers.

 

[trqmnstr]

Buff, how would a pin get bent like you say if they are connected? Just curious. I haven't unplugged anything so there's no chance that I did it. Also, where do I buy the dielectric grease? Thanks for the responses! Clay

 

[trqmnstr]

Help

UPDATE: Just took her for a spin this morning. I let her idle for about 5 min and took off. The hesitation is the worst it's ever been. After it warmed up it seemed to go away for the most part but it's still there. I was watching my tach and whenever I was at a constant speed (55 @ 1600 - approx) the tach needle would shake whenever it hesitated. Also, I haven't seen any blue or white smoke and haven't gotten the dead pedal. I need some help guys. Thanks

 

[DLBurns]

Buff, how would a pin get bent like you say if they are connected? Just curious. I haven't unplugged anything so there's no chance that I did it. Also, where do I buy the dielectric grease? Thanks for the responses! Clay

I asked the same question when I picked it up at the dealer. I don't remember ever having that connection apart prior to having the problem. It may have been that way since new?? who knows.

Dielectric grease can be bought at most auto parts stores.

 

[trqmnstr]

Thanks Buff, I'll do some hunting tomorrow.