Help me figure out what sensors need to be replaced.


Dec 6, 2015
Been slowly going through the car and fixing the obvious stuff. Got several mechanical / maintenance issues addressed and now I'm on to fancy sensors.

I'm using an ALDL scanner from 1320 Electronics for my 1985 Regal T-Type. I know for sure the IAC and TPS need to be replaced.
  • IAC Reading at 225 will drop to 190's while driving, never goes to zero
  • TPS Reading 4.998 and never changes...ever. Tried adjusting and succeeded in getting a CEL.
I cleaned the MAF and it reads around 40 when at idle and seems to follow a good path, feel alright about this one. But if more logs should be done let me know.

O2 stays in the 400-500 range mostly with O2 counts +100, the sensor number seems okay but the counts seem high.

Vehicle Speed is way out of whack, in park at idle says I'm going 70+mph?? Will fluctuate while driving but never coincides with the speedo.

Engine Speed (RPM) normally reads 0 zero, I've seen it occasionally bump up to a real value but mostly just 0 zero.

Thanks for the help, I'm a newbie with these cars but feel comfortable with FI and ECM logging. If there are good values to watch and certain types of logs to gather I would appreciate the feedback. Thanks.

0 engine speed, and 87mph??
TPS wide open?
Suggest you get a Scanmaster and a Powerlogger.............
Thanks for the tip on contacting the scan tool vendor. John Wales at 1320 Electronics is a stud, replied to my email on the weekend within an hour...sweet.

Turns out the ALDL file on the website was bad, he pointed me to the correct one and now I'm getting reasonable values for all fields. TPS and IAC are out of whack for sure, but at least the TPS is changing when I move it and the values 'look' right.

Gonna mess with the IAC and TPS today, will post back the log results from a drive when I get those two working right. Thanks again.

Fiddled with the IAC today with little success, if anything the idle is higher now that I've goofed with it. :oops:

I did fix the low voltage TPS error I was getting, so win some lose some. Next step is to pull apart the throttle body and give everything a good once over. While in there I'll just replace the IAC, they are cheap enough to eliminate the potential issue.

I'm not too savvy with what is good/bad with these cars yet, so if you have any opinion on the logs lemme know:

Links to good reading material appreciated as well. Thanks folks.

Just clean the IAC and throttle body with carb cleaner. IAC is high and needs to be closer to 10 - 30 at idle. There are articles at the bottom of the page. Also put a 180 thermostat in the car - Duralast 15848 at Autozone. That works better; you apparently have a 195 in there which may be the stocker. If that is true a good cooling system flush is probably in order too on your spring cleaning list. Also a new Bosch O2 sensor - 12014 at Autozone also. That may help your readings. And a set of Autolite 23 sparkplugs gapped at .030.

Now you have plenty to do.
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Thanks for the tip on replacing the t-stat, I like the idea of running a lower temp. Also agree that a Flush is in order as well, I have some new hoses on order and will tackle that this weekend.

Found out an interesting issue with the 1320 Electronics ALDL scanner. "Detailed" logging puts the car in 10k mode which pushes the idle to 1000 RPM and retards the timing by 30*...damn it. No wonder I couldn't get the idle down no matter how I adjusted the screw. The extra RPM was likely screwing with my MAF and O2 readings as well so not sure the logs are valid.

Ran the car with "basic" logging and got the IAC down to the 20s, but then it dropped to single digits so needs another adjustment. Unfortunately TPS is not part of the "basic" logging so have to toggle back and forth. I need to talk to the vendor to see if more data is available in the non-10k mode, as of now it is pretty limited.

Thanks again for the tips.
Why didn't u go with the scanmaster or powerlogger ? they are both awesome scan tools that are made for turbo buicks .
Because ' soup for me without an ECM conversion to '86/'87. I have bigger fish to fry before the restomod gets to that, might happen at one point but not yet.
Loaded the log from this morning:

MAFs look low at idle, but that is likely from the low IAC values. Now that I can adjust it with confidence that seems fixable.

O2 is all over the place, I think that one just needs to be replaced.

BLM looks high but as I'm not capturing the TPS or INT values not sure if this is bad or not, I gotta check with the vendor on seeing if there is a way to capture more data but not be in 10k mode.

I did see an EGR vacuum flag pop up, so maybe the higher BLM is a lean condition from a leak somewhere. All together possible as the more I dig into the car the more I can see how neglected it was...poor girl.

I'm very new to these values so any input is appreciated. Thanks.

Drove today and had some good, average and bad.

The Good is the IAC and MAF numbers are better after adjusting the IAC and TPS again, sweet.

The Average is the O2 numbers just bounce all over and the BLM is still high. New O2 coming this weekend.

The Bad, tried to get a WOT pull to check numbers and tranny didn't like that at all. Was merging on the highway at 45mph in 3rd, gradually got to WOT and tranny felt slippy then decided that 2nd would be a better place to be. Car threw a "Torque Converter Clutch" code immediately...damn it. Got off throttle and limped to work.

Car has 92k miles on it, so tranny is due for a rebuild anyhow. I think my fixes upped the power and now that the car is running better it has exposed the slippage that has likely been there for a while.

**Side Note**
Sent a request to the scan tool vendor to see if some of the 10k mode logging values can be made available in non-10k mode. :crosses fingers:
When cruising at part throttle the o2 volts are supposed to jump around rich, lean, rich, lean In a never ending "closed loop" About .400 volts is stoich, lower is lean, higher is rich.
Thanks for the response. What is a good range for it to jump through if 400 is stoich?? I'm seeing values from 0 to 800+ with odd stretches of the same value followed by big swings.

Bummer that TPS is not available in the driving log for me to confirm what I'm doing, looking at RPM isn't enough. :sigh:
As far as TPS goes, check it with Key On Engine OFF at WOT (make sure your floor mat is out from under the pedal. your reading should be 4.40 or more. Then start the car and check the idle reading. It should be about .42. If those two are good, you shouldn't have to check TPS, especially when cruising.
And your O2's will jump all over the place while idling and cruising. Anywhere between 0-800 or more. Worry about your O2 reading when you're doing a WOT pull in 3rd gear. If it goes below 780, let off.

Does this scantool give you a KR reading?

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Where are you located? You may need to pay a visit to a TR technician to get you on the right foot? It helped me when I was new to the scene. Keep a running list of everything you are concerned with so you get everything taken care of in one visit.

Do you still have cracked headers? I read that in your initial post. If so alot of these things you are concerned with are unimportant until the car's basic health is solid.
@87-WE2, IAC and TPS are pretty good now. I'm just used to my old FI car that had way more logging data so I feel like I'm running blind. I'd love to see throttle, engine load and boost as those values are all very related. My brain also needs to be calibrated for turning O2 and BLM into something like AFR, not there yet.

Learning > me.

@John Larkin, I'd love to have a local resource to chat with. I'm in Colorado Springs near the Air Force Academy. I've been keeping an eye on a TR for about two years, besides the donked out garbage on CL and the occasional Monte SS I haven't seen much out here. Mostly Wrangler and Subaru country. If you have a line on any good connections that would be great.

I did contact Casper Electronics but they are several hours north of me and are new to the area with not many contacts built up yet. Also found a shop in Denver that seems to have done some good tranny work for TRs, but also a couple hours away.

As to the cars health, it needs some love for sure.
  • Valve Cover Gaskets
  • Vacuum Lines
  • Radiator Hoses
  • Belts
  • Turbo Piping
  • Headers
  • Exhaust
  • Misc trim and weather stripping
I have a quote from Kirban on the Valve job stuff but having some trouble sourcing all the Pipes, '85 is turning out to be challenging car to work on.

Was hoping to diagnose some issues while waiting on parts, but if that is a lost cause let me know. Thanks for all the help, this site has a wealth of information.
I don't know much of anything about hot air cars but there is a silver lining: post what you need in Parts Wanted. Hot air parts are not in high demand. I am willing to bet you can buy everything you need in good used condition there for budget friendly prices. Soft parts you will just have to match up at a local parts store or buy from - for sure hoses are not that exotic and they have them.