Help before I go back to tuner today
04-15-2016 | 08:09 AM
#1
Thread Starter
Teching In
Joined: Dec 2015
Posts: 44
Likes: 0
From: Near E-Town
Help before I go back to tuner today Here's the story:
Had a new cam, pushrods, springs, timing chain, oil pump, installed last week, drove truck home on Tuesday, it is a 5.3 LH9. New trans/ 2800 stall converter also went in, but those have been working fine. Here is my issue.
I didn't floor it on the way home from shop, but the truck felt low on power during part throttle. A 220/228 Pat G blower cam, PAC 1219X springs, and 7.4" BTR pushrods should show a noticeable increase in power compared to the stock cam which was 194/194. Also, it had a hard time idling, and was surging/hunting sporadically.
On Wednesday I ran it at E-town. It ran as fast as it did with the stock cam/transmission. I was extremely disappointed because there were no gains in ET or MPH.
I also do not spin the tires at all from launching from a dead stop, on the street or at the track. The truck has no bottom end power. If the cam was installed wrong, would it cause the loss of bottom end, or am I pushing my fuel system past it's limit?
Didn't do anything with the truck yesterday, but I did look at the truck this morning to see if anything was amiss. I found that the intake clamp to the throttle body was not tightened. My jaw hit the floor. That is a major vacuum leak. I don't know how the shop didn't catch this. I tightened up the clamp and the truck idled like normal when I started it. No surging/hunting, and much smoother.
I'm going back today to let them know what happened. I did check out a few things with my Ultragauge MX this morning. My long term fuel trims are 12 and 14, and my O2 voltage is between 0.7-0.8. I know now that my truck is running lean, and the tune that was done is incorrect for my truck because of the vacuum leak.
So possible problems are:
1. Incorrect tune due to vacuum leak
2. Cam installed wrong
3. Fuel system not adequate (sorta doubt this one, but not sure since I can't read injector pulse width with my Ultragauge)
4. Not tuned on dyno, wide band O2 with street tune (and I can already hear everyone saying get it on the dyno for a tune, which I will)
Please let me know if I am correct with what I am thinking. I need to know for sure when I talk to them today. Thanks for any quick replies, I am going this afternoon, East Coast time.
Had a new cam, pushrods, springs, timing chain, oil pump, installed last week, drove truck home on Tuesday, it is a 5.3 LH9. New trans/ 2800 stall converter also went in, but those have been working fine. Here is my issue.
I didn't floor it on the way home from shop, but the truck felt low on power during part throttle. A 220/228 Pat G blower cam, PAC 1219X springs, and 7.4" BTR pushrods should show a noticeable increase in power compared to the stock cam which was 194/194. Also, it had a hard time idling, and was surging/hunting sporadically.
On Wednesday I ran it at E-town. It ran as fast as it did with the stock cam/transmission. I was extremely disappointed because there were no gains in ET or MPH.
I also do not spin the tires at all from launching from a dead stop, on the street or at the track. The truck has no bottom end power. If the cam was installed wrong, would it cause the loss of bottom end, or am I pushing my fuel system past it's limit?
Didn't do anything with the truck yesterday, but I did look at the truck this morning to see if anything was amiss. I found that the intake clamp to the throttle body was not tightened. My jaw hit the floor. That is a major vacuum leak. I don't know how the shop didn't catch this. I tightened up the clamp and the truck idled like normal when I started it. No surging/hunting, and much smoother.
I'm going back today to let them know what happened. I did check out a few things with my Ultragauge MX this morning. My long term fuel trims are 12 and 14, and my O2 voltage is between 0.7-0.8. I know now that my truck is running lean, and the tune that was done is incorrect for my truck because of the vacuum leak.
So possible problems are:
1. Incorrect tune due to vacuum leak
2. Cam installed wrong
3. Fuel system not adequate (sorta doubt this one, but not sure since I can't read injector pulse width with my Ultragauge)
4. Not tuned on dyno, wide band O2 with street tune (and I can already hear everyone saying get it on the dyno for a tune, which I will)
Please let me know if I am correct with what I am thinking. I need to know for sure when I talk to them today. Thanks for any quick replies, I am going this afternoon, East Coast time.
04-15-2016 | 09:19 AM
#2
You can't base an assumption on the air/fuel tune just from one reading of fuel trim. You need to data log up to 4,000 rpm at varying rpm/loads to populate your LTFT VE table. For wide open throttle you will need a wideband O2 sensor to datalog air fuel ratio. The ECM is open loop at WOT so you won't have any fuel trim data. That being said - if the LTFT is positive (i.e. your VE/MAF tables are lean) the ECM will hold the positive LTFT values at WOT as a fail-safe to prevent a lean AFT. For this reason a tuner should always work the VE/MAF tables for positive LTFT to prevent an over-rich condition at WOT.
1. Yes, any air leak downstream of the MAF will affect the tune. Any air leak at any point in a forced induction system will reduce power.
2. Doubtful the cam is installed wrong if it at least made same power as stock cam.
3. Lack of fuel volume will show up under load & RPM. Use a fuel pressure test gauge while on a dyno to know for sure (or possibly video the test gauge while street driving).
1. Yes, any air leak downstream of the MAF will affect the tune. Any air leak at any point in a forced induction system will reduce power.
2. Doubtful the cam is installed wrong if it at least made same power as stock cam.
3. Lack of fuel volume will show up under load & RPM. Use a fuel pressure test gauge while on a dyno to know for sure (or possibly video the test gauge while street driving).