Tech Tip Quick Index

Boost: Low
Boost: High
Fuel Pump Install
Hood & Hatch struts
Minimum Air Rate Adjustment
Intercooler Cleaning
Missing Emblem
Oil Filter
Power Antenna
Serpentine Belt
Service Manuals
Steering Wheel Radio Controls
Turbo Inlet Tube


Although there are substantial differences between a stock Turbo TA chip and a stock Grand National chip, the ECMs are identical. Thus, any Grand National performance chip can be used in a Turbo TA with generally similar results.

Oil Filter

It is important to use the correct oil filter for the TTA. The horizontally-mounted filter must have an anti-drainback valve to prevent oil starvation at engine startup. GM recommends the A/C PF-1218. Until recently this filter was difficult to find, but thanks to GMC, who is now using it on their big V8s, the PF-1218 is widely and cheaply available and with an improved anti-drainback valve. PAS originally specified the Fram HP-4 oil filter, which is also a good choice. Finally, the smaller NAPA 1086 is an alternative for those who are concerned with clearance between the oil filter and idler arm.

For an in-depth look at these filters read Turbo Trans Am Oil Filter Comparison, submitted by John Pearcy.


Synthetic oil is recommended for turbocharged vehicles. Synthetics resist "hot soak" and "coking" of the turbocharger bearings, and at extreme temperatures have superior flow characteristics to conventional oils.

Minimum Air Rate (Idle Air Control) Adjustment

Proper Idle Air Control (IAC) Motor adjustment is essential. John Pearcy explains how it's done in this Minimum Air Rate Adjustment Procedure.

Intercooler cleaning procedure

Oil accumulation inside your intercooler significantly degrades its efficiency, and causes hesitation, rough idling and poor performance. Come clean with. Gino Rinaldi's intercooler cleaning procedure

Fuel Pump Install

Installing a new fuel pump in a TTA is an involved task, as the fuel tank is located above the rear axle & exhaust. Tom Chou's fuel pump installation procedure makes it almost fun.

"Barking" or "knocking" sound under acceleration

Check the serpentine belt tensioner pulley. Most likely it is making contact with the air conditioner pulley. The original TTA serpentine belt was slightly longer than optimal . GM recommends p/n 12399983 as a replacement. It is 16mm shorter than the original which yields an full inch of clearance between the tensioner and the a/c pulleys.

Air leak at turbo inlet tube, or inlet tube collapsed

The turbo inlet tube (p/n 12399984) is made of relatively thin plastic. Overtightening of the hose clamp will cause the tube to buckle. Once this happens it is nearly impossible to achieve an air tight seal with the stock tube. Here is a trick: cut a short (<1") length of 3" exhaust pipe and insert into the end of the inlet tube. It's a perfect fit and will allow much tighter clamping (thanks to Rich Melucci for this one.)

High boost pressure

Normal boost for a stock TTA is 16.5 PSI at wide-open throttle.

High turbo boost can occur for several reasons. Most often, it's due to a problem with the wastegate control hose assembly. This is a group of three rubber tubes, leading from the elbow on the turbo compressor outlet, the wastegate actuator, and the wastegate solenoid (on the right side valve cover) to a plastic "Y" fitting under the turbo. These tubes are exposed to heat and will eventually crack and leak. Once this happens there won't be enough pressure to open the wastegate, and overboost occurs. Severe or prolonged overboost can lead to engine damage in the form of blown head gaskets and melted pistons.

Low boost pressure

If your TTA is exhibiting low boost, the culprit is likely the plastic "Y", especially if the wastegate control hose assembly was recently changed. In the "Y", there is a metal restrictor which regulates the amount of boost pressure applied to the wastegate actuator. The size of the restrictor orifice is critical to proper wastegate operation. Originally, from the factory, this orifice was 0.040" in diameter.

The problem is the newer "Y"s have a larger (0.050") opening in the restrictor, which allows more pressure to reach the wastegate actuator. This in turn causes the wastegate to open sooner, which results in low boost pressure.The solution is to re-use the original "Y" with the new hoses.

Low boost will also result if the "Y" is connected backwards. Finally, if the "Y" was mistakenly replaced with a generic part there will be no restrictor at all, which results in very low boost of about 10 lbs.

Missing "Turbo" Fender Emblem

It has been noted some TTAs lack the "Turbo" fender emblems. The reason is that, after building the first 350 or so TTAs, PAS ran out of these emblems. So, all TTAs after approximately the first 350 were delivered without them.

The emblems were later shipped to the dealer for installation, along with a template to facilitate exact placement of the emblem. However, some dealers attached the emblems in the wrong position because they didn't use the template, and some didn't bother to attach them at all.

If you need to attach (or re-attach, as the case may be) your fender emblems, you can download a .gif version of the template here. It prints at actual size of 8.5"x14" at 300 dpi.

DOS/Windows users: Download .zip version of TTA emblem template.

Steering wheel radio control servicing

To remove the button pad:

1) Disconnect negative (-) battery cable.

2) Remove horn pad from steering wheel by gently lifting up on each side of the horn pad to separate the velcro attaching pads. Be careful not to pull out the electrical connectors.

3) Remove electrical connectors.

The button assembly has three cables. Perhaps one or more of the connectors has oxidized. The three lines contain power, data, horn, and panel light circuits. All but the data line goes through a set of commutator rings on the turn signal cam. The data line is optically coupled via an LED/phototransistor pair.

The turn signal switch receives the signals, and from there it's a straight run though connector C210 to the radio. The data line is an orange wire. But it may not be the data line, you may not be getting power somewhere. Do the buttons light up when the headlights are on? If everything looks okay then the data input on the radio may be shot. But usually it's a bad connection somewhere, or the button assembly is gone.

Hood & rear hatch struts

Sooner or later your hood & rear window hatch will begin to droop. The fronts are 14019157, the rears, 16604426. You'll need a T-50 torx bit and a friend to do the rears.

Power Antenna

Sooner or later, one problem that all late third gen f-bodies seem to have is a broken power antenna, and the TTA is no exception. Fix yours with Russ Salerno's Power Antenna Repair Procedure.

Service Manuals

TTA service manuals are available from Helm at 1-800-782-4356. Order p/n S-8910-F for the 1989 Firebird manual (about $90) and S-8910-FAE for the TTA supplement (about $8).

Alldata Corporation offers a CD-ROM containing either shop manual repair information or factory technical service bulletins for the 1989 Firebird, including all TTA supplements. Pricing is approximately $30 for the CD with either shop manual data or TSBs, or $50 for both. A parts number & labor supplement may be available in the near future.

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