Dropped hp; need opinioins, advise...
 

Hey guys,
Here's my situation. My car is a 94 with a stock engine, K&N cones, dp, mp, GReddy FMIC, PFS-PMC, RP fuel pump, J&S knock sensor. I previously dynoed at 307rwhp. Boost starts falling off from 14psi to about 10.5psi by redline, and still does, but that's not the problem. I have an Apexi AVC-R to install to see if that will keep the boost consistent. Anyway, I was on the dyno again today breaking in the O2 sensor for my newly installed GReddy AFR gauge, and, HOLY SHIT, my hp is down by 47 to 260rwhp! Changes? Well, I've only done minor changes to the maps on the PMC, added an RP fuel pump. Yesterday I also readjusted my TPS(I think it's bad). It had a fast hunting idle between 500-1000rpm until it shut off, so I just moved the TPS to a more acceptable idle, seems ok now.

So can anyone give a clue as to what may be wrong? Thanks.

Chris.

Forgot to add
 

The car doesn't feel abnormal in any way; no flat spots, missing, bucking, etc. Plugs are brand new NGK plat. 9s, wires are good.

My guess is that you monkyed with it too much. The TPS doesn't just move on it's own. If you had to mess with the TPS to get it running right then you are most likely masking something else like a vacuum leak. You may want to run through the basics again and try to reset your car back to the way it was before you began tweaking it. You need to reestablish your baseline in other words.

I know the TPS doesn't just move on it's own. I was driving for a couple hours the other night, all was fine. I had to come to a stop in traffic, when the idle started hunting as described above, till it shut off. Couldn't find any leaks or loose hoses. Only solution I found was moving the TPS to another position. Maybe the TPS is going bad?

Anyway, my original question was about my big drop in power.

BTW, engine has about 7k miles on rebuild.

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Did you adjust your fuel maps for the new fuel pump? If not that will make you run rich, which will cause a loss in power. I wouldn't think by that much but running rich will foul the plugs jiffy quick, which could have added to your problem.

Ok, just came back from the dyno shop. After analyzing my old dyno runs, one difference is not so obvious. As each run was made, the ambient temp recorded by the dyno went up by a couple of degrees to a high of 97F from 87F at the first run. You could see a linear loss of power on each successive graph. My old runs were done earlier in the year and the temps were consistently in the low to mid 80s. BTW, after analyzing the new runs, highest peak hp recorded was 272, not 260 as previously posted, I just missed that one, so it's a loss of 35hp, not 47. So, what do you tuning gurus think, +20F=-35hp?

dis1- some leaning was done on the dyno, some improvement was made, but not much to recover my lost 35hp.

BTW, does anyone know if TPSs SUDDENLY go bad?

Chris.

Shit, can't count... that should be +10F=-35hp?

Temp makes a big difference and I was going to mention it but forgot. And not only the air temp but also the temp of your car. Things can get heat soaked really fast. When I got dynoed (with no fan) my second run was 15 hp less than the first due to heat soak. Lastly dyno computers should correct for air temp and altitude. For example if you go to my site and look at my graph you will see that I made 290 hp after correction. Before it was 300. This was with pretty low temps so hp was subtracted. All together this could account for a difference of 25 hp.
cvs

Thanks, man I needed that.