Riddle me this........after looking at my scan, I noticed that my car does not go into open loop at WOT (4.65v on the throttle position sensor). It went from open to closed at warmup, but nowhere during my scan did it go back into open loop. This is a snapshot of the scan when I was putting the wood to it:
27mph vehicle speed
3550 RPM
4.65v TPS
159f coolant temp (does not seem right.....says about 185 in cockpit)
100f MAT
98.3 gms/sec Maf
5.91ms injector
145 BLM
128 INT
888mv o2
85 crosses 02
142 Load v
closed loop
I think this was a first gear stab on the on ramp....keep in mind that the pins are jumped during a scan on my car.
I have posted in scan and tune with little response. My car has no power over 4k and will not rev past 4300 rpm. Closed loop scans look great. MAF grams/sec never exceed 105. I am leaving a lot of power on the table here, obviously. 2 different chips, similar results. New fuel pump, filters. New injectors 19lb tuned with fuel pressure (44lb) and injector PW, similar results. Gutted cat with res tips. New ICM and coil. The car does nothing dramatic, idles great, excellent throttle response, just runs out of breathe. TPS has full range.
I am very new to scans and could use some help and ideas. The MAF topping at 105 is a big red flag to me. I think the MAF is fine, it is just measuring the actual air flow. I need some ideas and thanks in advance. Oh....i have the 85 870 ecm. I am not changing it, unless it is bad.

 

oink

 

By the way the data you have looks, I am inclined to say you have a clogged cat, or exhaust restriction of some kind. The lack of air flow gives it away along with lack of performance at high RPM.


Dave

 

He says he's gutted the cats, could it be a clogged air filter?

 

YaY! A response! Thanks.....but my cat is hollow. No muffs, just tips. I may attempt running open header to confirm this is not the problem. I would appreciate more theories! My KN is clean, i have inspected all intake ducts for birds nests, etc.

 

Before you drop headers , can you take a vacuum gauge and see what happens at wide open throttle under load? If you start building vacuum at high RPMs(when problem occurs) WOT that would confirm a restriction on the exhaust side.If that is OK, then check intake side, Airfilter etc. If you are still ok, then you have a possible MAF problem. Have done base engine stuff? Compression etc. A bad cam can give you similar results also.
Sorry to throw so much at you, but theres alot of variables.
I have been doin this stuff for 20 plus years professionally so I have been down this road before.

Dave

 

Thanks VB....using a vac gauge is a great idea and is very doable. I have done the WOT FP test many times also. I have "exhausted" the possibility of an intake or exhaust restriction pretty much. I am always willing to recheck. My engine is completely rebuilt, forged flat tops, stock 76cc heads (new springs), Summit TPI cam. I am running thin head gaskets. Mild porting and 19lb Ford motorsport yellow tops.
Cam was new, broke in properly and I add STP to my oil. I suppose it could be wiped out or defective, I need to check into this. Keep throwing things out....I want this solved before I begin my next round of upgrades (eddy intake, full siamese stock runners, XE256 cam).

I was hoping more could be derived from the scans. Obvious mechanical problems may not allow for this so I will keep looking. Intake gasket is leaking oil, so a partial teardown is very soon.

 

...... The Ford 19# injectors are smallish , since the stockers were 22# ... your datalog with BLM's at 144 indicates a lean condition ..... At WOT the computer does not necessarily go open loop it just disables learning and ignores the O2S ... the disparity in temp readings may be because the ECM uses a different sending unit than the gauge ... the cooler temp should actually richen the mixture ... sounds like you're doing your own tuning ... What program are you using ?

 

Yep , its VERY easy to forget the basics, I would do the vacuum gauge first, if it does what I suspect(gain vacuum at higher RPM WOT), then you have a problem, and it is probably base engine. If you cant get the air out , you cant get it in, AND vice versa. Keep me posted and feel free to PM me.

Dave


Whats the chances of cam timing being off??

 

I agree, but the o2 sensor is showing rich at that shot, and even lean you should still get airflow, which according to MAF he does not have.
The 19lbers are small though, especially with the mods he has.
This is going to get interesting me thinks!!

Dave

 

My stock injectors were 24#. I have raised the injector constant on the chip, as well as increased the fuel pressure. Though the BLM is 144, the o2 sensor voltage indicates that it is fat, as well as the ALDL flag (rich). I used to think this was my problem, until I did a global change on the pulse width, +16 percent. I am using Tunerpro RT. It has a stock 1F bin.

 

Not saying this is going to cure anything but the 159 temp your ECM is reading could be throwing a lot off if you engine temp is really 185.

 

The cam was not dialed in....just dot to dot on the sprockets. I just don't see the yellow tops going static, they are supposed to be good to 300 plus HP. I have no indications of going lean, (plugs look good and no knock) and my gas mileage hasn't been good since I played with the pulsewidth. My scans do not show knock counts, but I have a good ear for it. Also my VSS is not reading MPH properly....I hit 85 during my scan, and the highest it showed was 51MPH. Interesting indeed!

 

If you raised the injector constant, the ECM thinks they are bigger than they are. It will give a shorter pulse width than it needs.

 

I misspoke....there is no constant in the 870 tables.....you have to increase the pulse width a percentage....which I did in the PW vs load table. I also ran the stock chip at first with the 24 # table. I have always had the fuel pressure turned up....lowest it goes is 43# with the vac hose off.

 

Sooooo.....back to the scan. Am I fat or lean with a BLM of 144 and a 880 mv o2? My ALDL flag says Rich. Very low MAF flow. This is where I think we should be looking. A vacuum test is in order first. Then maybe I should look at the cam lift and timing. Does the PW look correct? I should show you guys the next shot of the scan......

 

880mv is rich at that point, but the injector mv looks low, the maf gph is low, which will shorten injector pw. looks to me like there is no airflow. I think you are on the right path.

Dave

 

880 is lean at WOT. At idle or cruise it would be rich. Normal driving it should continuosly cross above and below 450. WOT it needs to be low 900s and stay there. The 900s numeber is sort of a safe starting point but every car is different. Some may want 940, some less but 880, I dont see being rich at WOT.

 

Not exactly, An o2 is only going to make 1 volt max by design, anything over 500mv(0.5v) is on the rich side of the switch. By design there should be multiple switches above and below 500mv.That is a factor on how the processor makes ms decisions on the injectors. That is your switch count. At wide open throttle, you want to see a high mv over 500mv,I agree 880mv may be a little low compared to what you expect, but it is still rich,and with a lack of airflow(low MAF gph)you may be a little low. Now we are assuming that the MAF is correct. A vacuum gauge at WOT under load can verify that.remember if you arent getting the air into the engine you will not get it out,and that will skew alot of readings.

BASE ENGINE!!! It may be fine , but you have to start there. vacuum, compression, cam timing, etc.

Dave

 

I think you two are talking about 2 different things when you are referring to .880 as rich or lean. If your talking about cruise or 14.7, an .880 average is obviously rich. If you are talking about wot where the motor is searching for an aft around 12.6, the .880 might be lean. When I monitored my motor with a wideband, the narrowband 02 voltage was around .920 for my target wot afr of 12.6. I realize all motors are different and 02 sensor readings are different.