Engine down on power

#1

I suspected as much at Road Atlanta a couple weeks ago, but today at Roebling confirmed it. It’s likely related that it’s missing at low and medium rpms, but I can’t really detect whether it’s missing or not at higher rpms. CEL comes on at idle but then goes off and stays off once the rpms go up.

Traqmate says it’s about 15hp low.

I did some research tonight and tomorrow I’ll remove the engine and battery grounds, grind and replace. I’ll also check for vacuum leaks, and maybe swap out AFM and ECU. I’ll also figure out tonight how hard it is to swap out injectors, because I’ve got some others to try.

I have another coil I could try, but I hate blindly changing lots of variables all at once.

Questions:

  1. I read that a sonic jewelry cleaner is a good way to clean injectors. Is that a reasonable alternative to sending them out for cleaning and blueprinting?

  2. I thought I might take it to the local dyno. Sadly I have no baseline. Should their exhaust sniffer be able to resolve the mystery.

  3. Other ideas?

  4. Is it reasonable to be able to detect missing at 3k rpm, but not be able to detect it at higher rpms?

#2

Misfires at low engine speed but not at high engine speed is frequently the result of an intake leak. An intake leak can also cause a low engine speed lambda fault, which will cause a CEL at idle that goes off when the engine rpm rises.

Ignition or fuel problems can cause misfires, but problems there usually get worse with increasing engine speed. I’d tend to think this isn’t your problem.

A bad or mis-adjusted TPS will cause the engine to be down on power at WOT. If the DME doesn’t see the WOT switch close, it continues to run in closed loop mode rather than using WOT maps.

#3

Problem fixed I think. I pulled the AFM, cleaned both it and my spare and tried both again. No change. I put on a second ground wire and surfaced the big ground between frame and oil pan. No change.

Then I spotted the problem. The throttle assembly was not being pivoted all the way by the gas pedal. There was some false starts as I worked on various theories as to why the heck the gas pedal didn’t pivot the throttle enough, but the problem only became clear once I took a good look at AL K’s throttle assembly. There is a 1cm long vertical pin about 4mm dia that anchors the throttle cable to the throttle body and I didn’t have one. Eureka.

So the whole problem yesterday was dumb and cost nothing to fix, I was only at 3/4 throttle. Woohoo.

Jim, show me the WOT switch at RA next weekend. I get it confused with the ICV switch.

I never did get decent times this weekend. By the time I had some power my ebay tires were so worn out I coldn’t hardly stay on the track. Turn 9 was killing me. It felt like I was drifting thru the whole damn thing.

But I had power. When you next see me, I’ll have my less shitty ebay tires on, and I’ll have better then 3/4 throttle on tap.

#4

The WOT switch and idle (aka ICV switch) are both in the TPS that is mounted under the throttle body. The TPS should be set so that the idle switch closes when the throttle stop is 020-060" off the stop screw. With the throttle on the stop screw the throttle cable is adjusted to just eliminate any slack. Then the accelerator pedal stop (behind the pedal is adjusted so that the throttle just reaches wide open when the pedal is all the down against the stop.

Having driven your car around the paddock, I’d say that it really needs a new throttle cable.

#5

No doubt about it. I think you need a new engine.

#6

csrow wrote:

Too funny,stop, I just made an unintentional mess on my computer

#7

rackeu wrote:

[quote]csrow wrote:

Too funny,stop, I just made an unintentional mess on my computer[/quote]

Chi is a lot nicer in person. Somehow the Internet brings out all this anger and meanness.

#8

Ranger wrote:

huh? I’m just trying to help you from going down the wrong path of fixing this problem with a simple missing pin. Remember the K.I.C.C. principle.

#9

this does seem altogether too simple a fix for you scott :slight_smile:

#10

kishg wrote:

As a witness to the process I can attest that this was absolutley the simplest solution ever for Scott.

However, it did take him a day and a half to get there.:slight_smile:

#11

The last I heard is that Ranger is going to add a pressure transducer and a laser optical detector to the pin with a 5 digit LED display and a large amber warning light in the cockpit.

This way, he will know how much pressure is being exerted on the pin during a hard downshift and if the pin is about to come out again.

#12

I envision Scott’s interior to one day resemble an Apollo capsule with lots of lights, analog gauges, and vaccuum tubes.

#13

Yeah, and it will take him 30minutes in the paddock and 20 minutes on the grid to run through the engine start and ready to roll check list.

#14

My daily services providing comedy relief should be compensated with an appropriately generous stipend. I lean towards good beer and short skirted serving wenches.

#15

To dream the impossible dream…

What you are likely to get is the cheapest beer that can be found served by Al Taylor.

#16

jlevie wrote:

[quote]To dream the impossible dream…

What you are likely to get is the cheapest beer that can be found served by Al Taylor.[/quote]

That being the case, I withdraw the short skirt requirement.

Actually tho, I owe Al, not vice versa.

#17

IndyJim wrote:

Hey, have some sympathy for his Enduro co-driver. I needed a 30-minute briefing last time I got in the car… :blink:

#18

Geegar has an interesting theory on that topic.

If it takes you longer than 1 min. to “explain” to someone how to drive your car, it is a POS…

It was forumlated I believe for street cars but there is a lot of truth in those words.

#19

IndyJim wrote:

[quote]Geegar has an interesting theory on that topic.

If it takes you longer than 1 min. to “explain” to someone how to drive your car, it is a POS…

It was forumlated I believe for street cars but there is a lot of truth in those words.[/quote]

where does push-starting figure in to that theory? :wink:

#20

You needed the malfunctioning (and illegal) push button start to see that Craig’s car was a POS?

You may want to see an eye doctor…